a main body, being integrally formed of one piece, including a cylinder and a handle connected to the cylinder, the cylinder having a chamber thereinside, the handle having a passage in communication with the chamber;

a piston, movably received in the chamber;

a blocking member, connected to the cylinder;

a rod, connected to the piston and extending through the cylinder; and

a reinforcement member, wherein the reinforcement member is assembled to the main body and abutted against and between the cylinder and the handle.