The C339SP Grab Clamp with Spinning Pulley from Avenger is a pincer jaw clamp designed to fit a variety of round or square pipes, beams, and bars for supporting TV and theater backgrounds. The clamp is equipped with a push-button lock for extra safety and 3.9" pulley for raising curtains or other articles in a theater environment. A testament to its zinc-plated steel construction, the clamp can support up to 331 lb.