The unicender is the most versatile mechanical prusik out there. It works great in single and double rope technique. Being mid line attachable, it is the fastest device on and off the rope. There is virtually no sit back, making it the most efficient ascender/descender during ascent. This technique shows how using a flip line as a chest harness the unicender becomes self advancing. With the addition of a knee ascender (Saka) and a foot ascender, you can go up the rope like your going up a ladder. It's my favorite way to get up the rope in single rope technique.