cylinder 46 the piston 58 is sealed to the rod 56 by an o ring seal 55 and to the cylinder 46 by an o ring seal 57 by this arrangement any differential pressure on the piston 58 moves the piston as will be described below with regard to the operation of the system the guide rod 56 retracts into a bore 60 when the wedge 50 moves down into a locking position the bore 60 extends below a bottom shelf 61 on the cylinder 46 the end of the guide rod 56 is chamfered to mate with a countersink ledge on the entry into the bore 60 for ease of mating of the guide rod 56 with the bore 60 further the interior surface of the cylinder 46 has a hydraulic braking chamber 62 to prevent the piston 58 from slamming into the shelf 61 the actuator is further provided with a sequencing valve 64 the sequencing valve 64 ensures during an operation to retract the ram 12 i e to withdraw the tail rod 28 into the bore 48 that the wedge 50 is properly aligned in the full up position as depicted in fig1 before porting pressurized.