Good day. I want to bring to your attention an overview of descenders for organizing rappelling. This review is my personal subjective opinion, formed due to considerable experience in climbing and working as an industrial climber.
I have at my immediate disposal three triggers, the rest I just happened to use.
The simplest and most well-known escapement of the "eight" type. 
Depending on the size of the holes, it can be used on both single and double ropes with a diameter of 8 to 13 mm. In the model shown, the small hole can be used for descending thin ropes and for belaying.
The advantages of this device:
1. Simplicity.
2.Strength.
3. Reliability.
4.Does not require maintenance.
5.Multifunctionality.
6. Light weight.
1. Spins the rope.
2. In some models (for example, as in the photo) there is no mustache for fixing the rope, which in turn complicates hanging on such a descender.
My favorite trigger is from petzl PIRANA. Despite its similarity to the figure-eight, this device was developed by petzl specifically for canyoning, which brought some good innovations to its design. 
For reference: Canyoning (eng. Canyoning or Canyoneering) - overcoming canyons without the help of floating facilities (boats, rafts, canoes, kayaks, etc.) using various techniques for overcoming complex water-rocky terrain: rock climbing, rappelling, jumping into the water , swimming.
When passing canyons, climbing technical equipment is used: ropes, carabiners, safety harnesses, descenders, helmets, etc.
The advantages of this device:
1. Simplicity.
2.Strength.
3. Reliability.
4.Does not require maintenance.
5.Multifunctionality.
6. Ability to work calmly on a wet, dirty, icy rope.
7. The ability to work calmly when descending with a lot of weight.
8.Very easy fixation of the rope to stop and the same easy extraction.
9. Light weight.
Disadvantages of this device:
1. Spins the rope.
Trigger device type "Basket". 
A very light and comfortable descender that allows you to work equally comfortably on one or two ropes. As long as you have a secure anchor point for your rope, this little guy will fly you the distance you need in just a couple of seconds.
In my opinion, the most convenient device is a descender that can be used for belaying on a rocky route.
The advantages of this device:
1. Simplicity.
2.Strength.
3. Reliability.
4.Does not require maintenance.
5.Small weight.
6. Does not twist the rope.
7. Very comfortable work on two ropes.
8. The ability to work calmly on a wet, dirty, icy rope.
Disadvantages of this device:
1. There is no way to hover (hover securely) at the required height without using other devices.
Trigger device "Lattice". 
Perhaps I'm going to overdo it a little, but at most it's a little bit if I say that this is the favorite descender of almost all cavers. I don’t like him very much, but this is probably more due to my misunderstanding of him and the fact that I am not a caver. A large number of my friends have been using its various modifications for many years, and I hear only positive feedback from them.
The advantages of this device:
1. Simplicity.
2.Strength.
3. Reliability.
4.Does not require maintenance.
5. Does not twist the rope.
6. Very comfortable work on two ropes.
7. The ability to work calmly on a wet, dirty, icy rope.
Disadvantages of this device:
1.Dimensions.
The next device has so many popular names that I'd rather take SIMPLE, known to all speleologists. 
This is the little brother or sister of the petzl stopper. The SIMPLE is quite a handy device for long descents on a single rope. Due to the absence of protruding elements and parts, it is very convenient in narrow places. But for me, that's where the positives end.
The advantages of this device:
1. Does not twist the rope.
Disadvantages of this device:
1.Dimensions.
2.Weight. (not very hard but I would like to feel better)
3. Lack of ability to use as a device for insurance.
4. It is not possible to hover (hover securely) at the required height without using other devices.
5. There is no possibility to work on a double rope.
6. Requires care.
Stopper from petzl. 
One of the most popular caving descenders in the world. Allows good control of the speed of descent. Can be attached to the rope without snapping off the harness thanks to the spring clip.
The automatic brake system is activated when the handle is released.
It is possible to climb the rope without changing the position of the device, using a leg loop and a jumar.
The advantages of this device:
1. Does not twist the rope.
2. The ability to calmly work on a wet, dirty, icy rope.
3. Ability to hover (hover securely) at the required height without using other devices.
Disadvantages of this device:
1.Dimensions.
2.Weight. (not very hard but I would like to feel better)
3. Lack of ability to use as a device for insurance.
5. Requires care.
Automatic belay (downhill) device GRIGRI 2. 
Forgive me lovers of bells and whistles, but I never understood him and never will.
Description from the manufacturer's website:
Belay device with automatic lock for ropes from 8.9 to 11 mm.
The GRIGRI 2 auto-lock belay device is designed to make belaying easier. The GRIGRI 2 works equally well for both leader and top belay. The device can be used with all single dynamic ropes from 8.9 to 11 mm (ideal for ropes from 9.4 to 10.3 mm). Compact and ultra-light, the GRIGRI 2 will serve you faithfully in your climbing activities around the world for years to come. The new design of the GRIGRI 2 provides better control during the descent.
The belay technique is identical to the classic belay systems: both hands on the rope. The fall is stopped by holding the free end of the rope.
Blocking: In the process of stopping the fall, the belayer holds the free end of the rope, the cam turns and grabs the rope, increasing the degree of blocking until the rope slippage is completely stopped.
The new design of the GRIGRI 2 provides excellent control during the descent. One hand holds the free end of the rope while the other hand depresses the handle to unlock the cam. The patented handle design allows for very smooth etching of the rope. Combined with the strong blocking action of the cam, this provides a feeling of complete control when descending.
GRIGRI 2 is compact and ultra-light: only 185g (25% smaller and 20% lighter than the previous GRIGRI).
The design of the device includes a stainless steel brake plate and cam to ensure a long product life.
For use with single ropes from 8.9 to 11 mm in diameter (ideal for ropes from 9.4 to 10.3 mm).
Schemes for installing the device on a rope are engraved on the device (on the outside and on the inside).
And now I will scold this miracle of technology. Personally, I absolutely did not like working with him, although perhaps it's all a matter of habit. It was very uncomfortable for me to give out the rope to the leader, if you do it with even the slightest jerk, the rope will be immediately clamped.
The advantages of this device:
1. Does not twist the rope.
2. Ability to hover (hover securely) at the required height without using other devices.
3. Convenient for belaying the second in a pair.
Disadvantages of this device:
1. Abundance of mechanics.
2. Demanding on the rope!!!
3.Weight.
4. It is not possible to work on a double rope.
5. Requires care.
Let's start with the equipment list.
We will need:
Suspension system.
I use Petzl Corax, but you can get by with a more budget-friendly Vento.
Descending device. I use a vent basket and a horned figure eight.
Approximately three locking carbines per person.
Two pieces of rope 25m and 10m. I use 10mm diameter static
Gloves so as not to burn your hands.
The photo also includes knee pads and elbow pads.
The boots were never used. Instead, I climbed Lowa Zephyr.
Set for two people, me and my wife.
All this, including a thermos with tea, was put away in a trunk.
Now I will tell about each element in more detail.
Suspension system.
Petzl is still a brand with a worldwide reputation, which is why I bought it. I don't have much experience, but overall I like it. Wide, comfortable waistband and leg loops. Large range and very easy adjustments. Lots of hanging points for accessories. In short, a great choice.
Rope - domestic static 10mm diameter. In order to attach to the anchor point, you need to learn the figure-eight knot. It is simple, but very strong and practically does not weaken the rope. The order of knitting in the photo.
The tied knot looks like this.
Next, a carabiner is fastened into the loop. With this carabiner, you can attach yourself to various hooks, embedded parts, lugs, anchors, etc., but this is not very safe, because. fasteners may be rusty and not very reliable.
The most reliable fastening is for monolithic objects, reinforced concrete. supports, large channels and I-beams, then with the help of a carbine a sliding loop is made, with the help of which the fastening takes place.
I have seen two types of carabiner fastening into the system. In the central ring or simultaneously in the loops of the waist and leg loops. Petzl explicitly states that the carabiner must be clipped into the ring.
So far I have used the Ventovsky basket and the horned figure eight. I'll start with the bow.
Its advantages:
- does not twist the rope.
- convenient to use.
- can be used as an automatically blocking insurance (but more on that another time)
The cable on this SS can only be used for transportation, it cannot be loaded.
For use on a rope, make a loop and thread it through the DR so that the free end of the rope passes through the jaws of the device.
By pulling the free end of the rope up, we select the slack.
We start a hand with a free end behind the back, pulling the rope. Everything can be posted. The descent is made by slightly relaxing the hand with the rope.
The figure-eight descender works in a similar way, but it twists the rope, which is not convenient on long descents.
There are two ways to attach the rope to the figure eight.
The first is through a carbine.
This method creates less friction, resulting in a higher descent speed.
The second way is through the neck of the SU. More friction and less speed.
Similarly, we choose a basket of slack and wind up a hand with a stretched rope behind our back.
A feature of the horned figure eight is that you can fix the rope on it and free your hands.
Some moments of self-insurance.
There is always some chance that you will let go of the rope from your hand, and the SU will immediately release the entire rope and you will fall. To avoid this, there are various ways of insurance and self-insurance.
I'm using the "autoblock" node. It knits as follows.
For this knot, I use a standard 60cm quickdraw.
We fix the guy with a semi-grasping knot (noose) on the leg girth, hang a carbine next to it.
We wrap the quickdraw 4-6 times around the rope.
Then we snap it onto the carabiner. All. The node is ready.
In the event of a breakdown, you will hang on this knot and not fall. At the same time, the hand must be kept between the SU and the autoblock while adjusting the speed of descent.
Now to practice.
First. We get up on the "windowsill" from where we will go out, select the slack of the rope and pull it.
From a different angle
For the first trials, insurance and an insurer are required. In the photo, the safety rope is green. One end is tied to the system, the other is passed through a fixed carabiner and hung out. The insurer gives out a green rope, and in the event of a breakdown, does not allow him to fall.
Because the wooden surfaces of the window sills create a lot of friction I insure across the back. In case there is almost no friction, it is worth belaying through the descender on the system.
In principle, you can master the descent in a fairly short time, maybe a couple of hours. Then everything goes like clockwork.
I hope this article will be useful to you. In any case, thanks for your attention.
Remember about safety and liver tea.
The figure eight is usually the first descender that climbers master, it is simple as an ax and reliable as a crowbar. In addition, the figure eight can be used both for insurance and as a ring, in general, which is enough for imagination. Let's talk about her.
Varieties
Now there are a huge number of eights of different functionality on the market, some of these descenders are no longer similar to the "8".
All eights can be divided into two groups, with and without horns. The horned figure eight is convenient where you need to hang and free both hands, the hornless ones are simply lighter and are considered more athletic.
Modern versions of this descender also offer different ways to thread the rope into them for different speeds of descent and for show-offs.
There is a variety of eights with a rectangular large hole, this is necessary to eliminate the twist of the rope during the descent. It was because of the strong twist that eights were banned for use by cavers during the descent.
There is a variety called "Nine". It has a more advanced locking method, but it is not clear how to safely use it during the descent. After all, for this you need to loosen the free end of the rope going to the hand. How?? Only if you pull yourself up with one hand on a rope that goes up. If you know how to safely block it, write in the comments. But, in addition to the new blocking scheme, this “nine” also has classic horns, although they are short, but you can use them. I think it is well suited for promalp, where long hangs are needed.
There is a figure eight from Petzl with a special overlay to take it with your hands when it is very hot. This is strange and incomprehensible. Let me explain, when descending, the figure eight heats up so much that it can burn your hand .. But for some reason the manufacturer didn’t think about the rope, but if it melts, then at best you will hang on the insurance, and at worst, I think it’s clear .. Personally I control the heating during the descent, and if the figure eight for the hand is hot, then I reduce the pace a little.
There is also a figure eight called "Petal", this is an interesting variety. It is very compact and has one horn and notches at the top to block the rope.
Application
When it comes to descending, there are several ways to thread the rope into a figure eight.
First way- through the neck of the figure eight, without snapping the rope into the carabiner. With this method, the friction of the rope is higher, and hence the speed of descent is lower. It is also easier to hold the free end of the rope. The downside is that for such a rope filling, you need to snap off the figure eight from the carabiner.
Second way- through a carabiner and a larger hole of the figure eight, with this method the highest speed of descent and the smallest twist of the rope are achieved.
There is another way, but you should never use it. Look at the photo below. Once again, do not use this method, I am talking about it only so that you know that it exists and that it cannot be used. This is life threatening, you can just lose the rope and continue almost free flight.
Other methods require non-standard figure-eight configurations, and they are not particularly needed.
The best way to descend is the second one, it is the fastest, there is no risk of losing the figure eight and rope twist is minimal.
figure eight horns
Separately, it is worth mentioning the use of the horns of the figure eight. They come from two sides (such a figure eight is called "Invar") and from one side. Needed to block the rope in order to hang and free both hands. Many simply wind the free end of the rope around the horns, but this is also not safe. That's right - after winding, additionally throw the free end through the chassis, look at the photo.
Double horns can be used for blocking when descending on a double rope and for zigzag descending.
Descent in a zigzag is when two ropes, 1-2 meters apart from each other, are simultaneously passed through a figure-eight with double horns. When descending, one rope is blocked by the horn, and the other is released a little, then the ropes are changed. This method of descent can be useful for promalp.
Alternative ways to use the figure eight
In addition to using the figure eight for its intended purpose, it also has other possibilities. For example, a figure eight can be used instead of a ring. If carabiners are snapped into it from both sides, then in some cases it can replace the quickdraw. Paired with a jumar, the figure eight can also be used to lift. However, for lifting, it is better to replace it with some kind of grasping knot. It is the figure eight, due to the lack of moving and shock-sensitive parts on it, that is best attached to a rope instead of a load for throwing onto a branch or somewhere else. And of course, the figure eight is used to insure a partner, because if he falls, it will be enough just to hold the rope.
With this article, Master Gumbs, I begin a series of materials about climbing pieces of iron.
It is not enough to climb a mountain or a building. From there, you still have to get off. Often, it is much more convenient to use a descender than to try to get back on your tracks, slipping and balancing. And in industrial mountaineering, in most cases, they get to the workplace by the descent method. It is far from always convenient to descend on knots. Yes, and "iron" offers a much larger number of use cases.
So - "eight"
.
One of the most common descenders, descending from the legendary Sticht puck. Naturally, having a bunch of options. The principle of operation is based on increasing friction. So, the classic figure eight increases the effort on the rope by 4-20 times. For example, if you hold the rope with your hands in front of the figure eight with a force of 25 kg, then behind the figure eight the force will be 200 kg, with a grip force of 50 kg by hands - 300 kg.
Due to the large number of kinks, a common disadvantage of all figure-of-eights is that they twist the rope. This can be somewhat smoothed out by preventing the rope from touching the ground.
Bicorn, horned
Classical and specialized ("Pirana" from "Pecel")
Horned figure eight (invar, puck)
Blocked eight. In the unloaded state, it is slightly offset towards the working hand, but if there was someone in the harness, it would become straight.
To descend, you need to take the free end in your hand (which goes down), and, slightly pulling, begin to drop the coils from the horns. When you feel that you have begun to crawl down, then everything is going as it should.
For a hundred kg of cargo, it is better to leave one turn on the horns. If, however, a person weighs 60 kilos, then you can safely dump everything. Naturally, not forgetting about holding the end.
And a correctly blocked eight)
But so few people do.
As a rule, this is a metal product that repeats the figure "eight" in shape. Two rings are inextricably linked with each other, one is less than the other at least one and a half times. On the one hand, there are two protrusions in the form of horns, intended for blocking, by wrapping with a rope, up to 5 ogons (turns) are performed. You can try more, but it will not fit))). For additional blocking, the free end can be passed between the figure-eight and the stretched part of the rope.
It is used in mountaineering, promalp and organization of show-offs. It is used for descent, and in mountaineering / rock climbing, also for insurance
For mountaineering, aluminum is most often used, in industrial use steel is more often used.
In the first case - to reduce wearable weight, in the second - for durability. After 50-60 descents on a contaminated rope, the duralumin "eight" is produced by about a third, becoming completely unusable.
Steel, on the other hand, lives for two or three seasons, while the Moldavian-Central Asian brigades live up to ten
Rope threading options. On the left - a variant for lightweights. On the right - for good people, who should be many.
I think that the relationship between the method of refueling and the weight of the descent body is noticeable. For ensigns, I suggest:
The rope passing through the carabiner and figure eight has fewer kinks, and, accordingly, creates less friction. Less friction - faster descent speed. Everything is simple.
With this option, the rope passes on the other side. There are no major changes involved. A matter of habit, nothing more. Personally, I prefer the right one.
There is also such a refueling option. Also, it doesn't change anything.
Despite the fact that the origin of the name is clear from the design itself, I once heard a version that the figure eight got its name due to the fact that with additional blocking, the turns on the horns intersect.
Classic figure eight (hornless)
It is used in mountaineering and rock climbing to organize the descent. It is not intended for hanging, because there is nothing to block the rope. Unless, one more carbine to fasten, and throw fires through it. well, or wind up ingenious knots.
During factory production, it is made of aluminum alloys.
On the left - the position for uncontrolled descent :)
On the right is the working position. The lower end, like all eights, must be controlled by hand during the descent.
Specialized eights.
There are a huge number of options designed for the most diverse specializations in the world. Unfortunately, I have at hand only Petselev's "Pirana" without a corresponding carbine, therefore, a detailed story will not work.
To be continued
Materials and types
As a rule, this is a metal (aluminum alloys or steel) cast part, repeating the figure eight in shape. Two rings are inextricably linked with each other, one is one and a half times smaller than the other with an inner circle diameter of up to 50 mm.
The use of the eight for insurance
The figure eight is used for insurance during the descent and ascent of a participant with a heavy backpack, an injured person with an accompanying person, etc.
When belaying, the figure eight is fixed on the upper point, with a small ring to the base carabiner. The rope passes through a large ring and wraps around the neck (see illustration 1). The participant on the belay stands on self-belay and holds the rope on opposite sides of the eight, giving out or choosing the rope as he moves and making sure that the carabiner is tense.
The use of an eight for descent (rappel)
- When descending slowly, descending with a backpack or load, or when descending a heavy load, the rope is thrown over the neck of the eight, which increases friction and slows down the descent (see illustration 1).
- During high-speed (sport) descent, the rope is passed through the carabiner (see illustration 2).
- You can also use the descent method, in which the figure eight is automatically fixed. To do this, the rope is twisted 180 ° counterclockwise and thrown over the neck of the eight. When descending, one hand of the participant must constantly hold the lower part of the rope. With the other hand, the participant releases the eight from fixation by turning its small ring down. If you raise the ring or just let it go, the rope will pinch and the descent will stop (see illustration).
This method of insurance (see illustration 3) is fundamentally dangerous and is not recommended for use. Leaving the rope off the small ring will result in complete loss of rope control and an uncontrolled fall.
Links
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See what "Eight (device)" is in other dictionaries:
Eight is a noun corresponding to the number 8. Eight (boat) boat in rowing. "Eight" unofficial name VAZ 2108, Audi A8; as well as any eight-cylinder engine. "Eight" appearance of an endless tape ... ... Wikipedia
Eight Eight (device) device for organizing insurance and downhill skiing Eight (knot) knot used in rock climbing and mountaineering ... Wikipedia