Set-up: Find a railing, sturdy door frame, or other suitably stable object to hold onto. Set up next to it, standing on the working leg with the resting leg extended straight out in front of the body.
Movement: Descend as far as possible while maintaining body-control and knee stability. Return to the starting position. Use the the stabilizing object together with your off-leg for support. Over time, attempt to use less and less support until you need none at all.
Repetitions: Perform all prescribed reps on one side, then on the other. This counts as one set.