To conduct the rescue work for victims by using either a gas or a liquid such as propane, high-pressure oxygen or city water pressure, not limited to compressed air.

An inner tube cylinder 2 is inserted into a jack outer tube 1, and the lower end section of the inner tube cylinder 2 is closely connected to a base 4 by screws 18. An air vent hole 12 is bored near the upper end of the inner tube cylinder 2 as the relief valve of a safety device. A booster valve 13 and a pressure discharge valve 14 are stuck to both faces of the base 4, and an antislip O-ring 6 is stuck to the lower end face of the base 4. The inside of a piston 3 is made hollow, and a female screw 8 is provided on the inside. The female screw 8 is meshed with a male screw 9 installed on an adjusting bolt 5, and the operating height of a jack is adjusted by this adjustment. The piston 3 is inserted into the inner tube cylinder 2. The upper end of the piston is integrally fixed to the inner face of the upper section of the outer tube 1. The height adjusting bolt 5 is inserted into the hollow of the piston 3 via the meshing of the female and male screws 8, 9.