The figure of eight descender is the cheapest around, and so is fairly popular. Unfortunately it is also very dangerous in a canyon where the bottom of the rope is not hanging free. The problem is the way the rope twists around the descender: it twists the rope badly and you end up with a bundle of kinks and tangles. If you get one of these jammed in your descender while you are half way down you are in big trouble. It is equally possible to run into the problem at the bottom, when you take your weight off the rope. Just as you do so, the twists tangle around the descender and you find you can't get enough slack to disconnect from the rope. If you are floating in the water under a waterfall when this happens, you can be in trouble again.

One way of handling this is to always carry several prussik loops in your pocket or on the back of your harness (out of the way!), and to know how to use them. They can let you can take your weight off the descender while you sort out the mess. You need to have practiced using prussik loops beforehand of course.

This problem is so severe that many clubs do not permit the use of figure of eight descenders on club trips. They prefer the use of "in-line" descenders, where the rope is not twist around. The various "Rack or Stop" are strongly recommended instead, like the one to the right.

Stop

Special self-braking descender for single rope that locks as soon as your hand lets go of the lever. Ideal for long controlled descents.

Self-braking system operates when the handle is released.

The rate of descent is controlled by varying the grip on the free end of the rope.

Rope climbing is possible without changing the position of the STOP by adding a foot loop and a handled rope clamp / grab.

Spring clip allows the rope to be inserted without removing the STOP from the harness.

Technical specifications
For use on single ropes from 9 to 12 mm

Rack

Allows the friction to be varied when the descender is under load to adapt to changing conditions (rope weight, terrain, etc).

The number of bars engaged on the rope may be adjusted at any time to obtain the desired amount of friction.

Good distribution of friction and heat helps preserve the rope.

Does not twist the rope.

Technical specifications
For use on a single ropes (9 to 13 mm) or double ropes (8 to 11 mm)