Openable even when attached to the anchor, the SPIN L1D pulley is designed to be used in conjunction with a descender for maximum simplicity in setting up a deviation for a heavy load. The faceted sheave only rotates in one direction, providing excellent efficiency when hauling and adding friction zones for the rope for additional braking when lowering. The swivel facilitates handling, allowing the pulley to be oriented under load, and direct connection of carabiners, ropes or slings.