Slide and lock clamps for attaching to supports are provided. In a general embodiment, the present disclosure provides a clamp including a base plate comprising a first cradle. A rod is secured to the base plate. A sliding carriage is movably connected to the rod. The sliding carriage includes a lever, a cam, and a movable lock constructed and arranged for releasably locking the sliding carriage in place on the base plate. A second cradle is movably connected to the rod and positioned next to the sliding carriage for securing a support between the second cradle and the first cradle.