A hand tool or clamp, which locks itself to a work-piece to thereby free the hands of the user, includes a fixed jaw secured to one end of a slide bar and a movable jaw mounted to the slide bar for movement therealong toward and away from the fixed jaw. The movable jaw is normally spring-biased toward the fixed jaw by a flat coil spring supported on the fixed jaw and connected at its free end to the movable jaw. The spring is uncoiled as the jaws are pulled apart to receive a work-piece, and when either jaw is released, rewinds and rapidly advances the movable jaw along the slide bar into clamping engagement with the work-piece. Additional clamping pressure is provided by a screw mechanism associated with the movable jaw which cooperates with the slide bar to advance the movable jaw toward the fixed jaw and increase the clamping pressure between them.