Abstract: A pneumatic or hydraulic cylinder (10) having a bore (12) cooperating with a piston (18). Extending from the piston (18) is a piston rod (37). There is further provided a pawl (26) which is engageable with the piston (18) to retain the piston (18) at a desired location. The pawl (26) is moved from engagement with the piston (18) upon fluid under pressure being delivered to one end of the cylinder (10).