The drop hammer has simple running, the whole set after hoisting is screwed to rods. After removing safety pin, the outer tube can be raised together with the hammer. At 2 ft 6 in height, the cam makes release of hinged hooks so that the hammer may automatically fall on the drive-head. The lifting mechanism is then lowered, the hooks re-engaged on the hammer and the procedure can be repeated as by need.
This procedure developed by Terzaghi and Peck gives the measurement of the penetration resistance of soil, with the use of a standard sampler driven for 1 ft with a hammer of 140 lb, dropping 30 in.