Abstract: A lock utilizing a retractable pin is used to capture one link of a chain to fasten the chain to one or more vertical uprights. The user depresses a bolt that protrudes from the hollow vertical stake member to overcome spring tension and slide a hardened pin away from a slot in the stake and an aligned slot in the lock housing, then inserts a selected link of a chain and releases the bolt, which slides the pin through the chain link and beyond the slots. The pin reciprocates within a tight-fitting bore in the lock housing, increasing lateral strength of the locking system. The resulting railing can cover any length and a number of spaced parallel railings can be strung between spaced vertical uprights.