Not mine, Kevin Bingham's. I've heard like most of you that Kevin came up with the idea from sharing the hitch friction using a "wrench". Anyone ever seen the wrench? I pictured a box end with a slot cut to pass the climbing line through but after more thought I'd guess he passed the climbing rope through an intact box end before setting a tip just to experiment, no slot needed. 5/8" maybe? Funny where the (my) mind wanders (when not in a tree).