The Garda Hitch also known as the Alpine Clutch is a class of climbing knots known as ratcheting knots for their ability to let the rope move in one direction, but not in the other. This class of knots has many uses in climbing and mountaineering, for example in a pulley system where a load is being hauled up a cliff, the Garda hitch prevents the load from slipping when the pulley system is reset.

The drawbacks to the garda hitch are that it is hard to release under load, it is hard to inspect, and it adds a lot of friction to a pulley system. Particularly difficult is to figure out which way the rope will run freely, and which way it will lock just by visual inspection.

The Garda requires two similar carabiner

Carabiner

A carabiner or karabiner is a metal loop with a sprung or screwed gate that is used to quickly and reversibly connect components in safety-critical systems. The word comes from "Karabinerhaken", meaning "hook for a carbine" in German.-Use:...

s, and works best with two identical oval carabiners. However, identical "D" carabiners will work, although there is a risk of the "D" carabiners unclipping.

Tying method

Attach the two oval carabiners to a sling or cord with both of their gates facing up and out in the same direction. If using "D" carabiners, attach them to a sling or cord so that they are next to one another with the gates opening down and out in the same direction. Clip the rope through both gates, loop the right hand side of the rope and clip it through the left carabiner. What results looks like a simple twist around two carabiners, but by pulling on the rope ends you can easily see how the hitch locks in one direction, but pulls freely in the other.

It takes a bit of experience to tell which end will run freely when pulled--it's the end that comes out between the two carabiners, 'spreading them'. This easily becomes intuitive, as the other end pulls the crabs together so they squeeze the rope between them, locking it: