Abstract: A clamp for fastening a plate to a pipe or other upright in which the clamp includes a generally U-shaped stirrup member with its arms positioned on opposite sides of the upright and the end portions of the arms defining a slit for receiving the plate. A lever member is removably supported by the arms for pivotal movement with respect thereto and is arranged such that a single pivotal movement of the lever member is effective to secure both the plate and the upright to the clamp and thereby maintain the plate and the upright in fixed relationship with each other.