This arm is one of those things I told myself to build. I keep needing it. The basic idea is that its a highly positionable arm that I can use to hold things, usually while I weld them in place. The design spec is for it to hold up to 10lbs out to 24inches. It definitly exceeds that spec. Its an ad-hock design (for making ad-hock designs) made from scrap metal, its truely amazing how a little grinding and paint can make something look really good.
Its found a number of uses so far, I expect to put a lot of wear on it. 
Every axis is locked by a threaded handle (the yellow ones). There are 6 axies on it.