The Stopper Knot. Used to prevent the rope from pulling through a belay or rappel device. There are many cases the stopper knot will prevent the rope from pulling through a device.
The stopper knot should also be used with the figure 8 and bowline knots. This knot will help prevent the short end of the rope from pulling through the knot. It should be used anytime the end of the rope could possibly be pulled back through a knot.
The stopper knot is easy to tie. It takes most climbers less than 30 seconds to tie the stopper knot. It is an important part of protecting the climber. Use the stopper knot to prevent the end of the rope from slipping back through the knot and untying. Also at the end of the rope during a rappel or belay. The stopper knot will prevent the rope from pulling through the belay or rappel device. Also see overhand knot for alternate sequence.