A prop consisting of two telescoping steel cylinders that are extended by hydraulic pressure that may be provided by a hand-operated pump built into the prop. The prop holds about half a gallon of mineral oil and is fitted with a yield valve that relieves the pressure when the load exceeds that for which the prop is set. A hydraulic prop enables quicker setting and uniform initial loading, and it can be withdrawn from a remote, safe position. The hydraulic prop was first used in a British coal mine in 1947.