Autoblock

The Autoblock is easily tied from a loop of accessory cord: just wrap the loop around the standing line several times, and clip the ends with a locking carabiner. It also works when tied with 9/16"-in Spectra® webbing (I suggest trying it with about 5 wraps to start). Many climbers use this knot as a rappel safety, a practice that I don't follow for a variety of reasons. The knot can be released under load by pushing down on the top coils. As an ascender knot, I find it works well, but one must pay attention to the coils to make sure that they don't cross. This can be avoided if the sling length is carefully chosen, but normally one ties this knot with whatever sling is handy - I've even seen people use a sling that still had a hexentric on it because it was the only one available!