Abstract: A safety clamp to which a workman's lifeline is connected, for removable and slidable attachment to a flanged structural beam. The clamp includes a pair of complementary U-shaped jaw members slidably coupled to a bar member disposed transverse the beam. A quick-release lock mechanism is provided each jaw member to releasably lock it to the bar member. Each jaw member is defined by horizontal upper and lower plate members interconnected by a vertical side member. Rollers or bearings are connected to the upper and side plates to reduce frictional engagement between the clamp and structural beam to which the clamp is connected, thereby allowing the clamp to slide along the beam. In an alternate embodiment the lower plate member is pivotally attached to the vertical side member for rotation. Such pivotal rotation allows the clamp to bypass such obstructions as beam attachment tabs without having to remove the clamp from the beam.