This is intended to be put on a tripod and hold your rifle for more stable shooting. I worked on this a while back and just remembered I hadn't put it up here. It needs some work, but does work as is.
A thumbscrew for tightening the "slider" would be better than a regular bolt.
A regular nut instead of a heat-set insert would be better for most people.
A rubberized surface where the rifle goes would help grip the rifle and keep it from slipping when tightening it.