Leveling Jacks. Designed for permanent installation, these screw-style jacks hold platforms and other equipment in place and stabilize them at the required height. Drill a 1¼" diameter hole through the platform to be leveled and bolt the platform between the upper and lower flanges of the jack's divided housing. Flanges are 3-5/8" overall diameter, 1/8" thick, and have (6) ¼" diameter mounting holes equally spaced on a 3" diameter hole pattern. Jacks are made of steel with a polished chrome finish and have an 8½" long handle that folds down when not in use. They stand on a 3-7/8" diameter swivel base that has a slip-resistant rubber pad on the bottom. Screw diameter is 1¼". Lift rate is ¼" per crank revolution. Specs: minimum extended height 4 1/2"; maximum extended height 13 1/2", 21 1/2", and 25 1/2" overall height 18", 26", and 30"; screw travel 9", 17", and 21".