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1U Standard Chassis 47U
A typical full-size rack is 42U, which means it holds just over 6 feet (180 cm) of equipment, and a typical "half-height" rack is 18U–22U, which is around 3 feet (91 cm) high. The mounting-hole distance (as shown to the right) differs for 19-inch racks and 23-inch racks: 19-inch racks use uneven spacings (as shown to the right) while 23-inch. Originally, the mounting holes were with a particular screw thread. When are too thin to tap, or other can be used, and when the particular class of equipment to be mounted is known in advance, some of the holes can be omitted from the mounting rails. Threaded mounting holes in racks where the equipment is frequently changed are pr.