Abstract: The invention relates to a jack-up platform locking apparatus. The subject locking apparatus includes a frame operable to be securely connected to a deck of the platform and a lock unit having at least one tooth for engaging a compatibly configured surface upon a vertically adjustable platform leg. Hydraulic motor means are provided for vertically adjusting the lock with respect to the deck and leg. An additional hydraulic motor is provided for horizontally actuating or deactuating the lock with respect to the platform leg. The invention further includes a mechanical assembly for vertically securing an engaged lock with respect to the platform deck. A reaction wedge member is provided for horizontally securing the lock in firm engagement with the leg of the offshore platform.