Abstract: A climbing aid having a rigid frame, two axles supported parallel to each other by the rigid frame, two pairs of cams pivotally mounted one pair per axle, and spring members mounted on the axles, which act to urge each cam into its extended position. The device clamps onto a rock protrusion such that the two pairs of cams are situated on the opposite sides of the protrusion. Initial force holding the device clamped comes from the spring members. Because of the shape of the cams, application of downward pull to the device translates into additional clamping forces applied to the rock protrusion. Application of pull onto a slidably mounted trigger actuates the cams into a retracted position, allowing the device to clamp onto protrusions of a range of sizes.