This is a Rigid brand pipefitter's TriStand which I picked up at a swap meet. It is a medium sized model, not the largest, and has a built in chain vise. Other models have swing-away clamp vises.
I like to use this for supporting a rear axle assembly for any and all assembly work. Every bolt is accessible and the axle can be completely assembled or disassembled on the stand. This is a lot easier than rolling around on the ground arm wrestling it like an alligator!