A threaded shaft extends from a base which has an inner and outer surface. A disc with an inner and outer surface is comprised of a resilient and slip-resistant material, such as emulsion styrene-butadiene rubber (E-SBR). The disc has a non-threaded opening which is slidably received by the threaded shaft, allowing the disc to slide toward or away from the base inner surface. A washer has a non-threaded opening that allows it to be slidably received by the threaded shaft, allowing the washer to move with the disc outer surface. A fastener, with a threaded opening, mates with the threaded shaft and reversibly tightens the disc toward the base inner surface. A section of tarp or other sheet material can be securely held between the base and the disc.