Complex sentence: The Bachmann (also spelt Bachman) is useful when the friction hitch needs to be reset quickly/often or made to be self-tending as in crevasse & self-rescue.
Split into simpler sentences: The Bachmann (also spelt Bachman) is a friction hitch. It is useful when the friction hitch needs to be reset quickly/often or made to be self-tending as in crevasse and self-rescue.