Hand (unit) inches for the handsbreadth; Mortimer gives the same, three inches for the Hand's-breadth, and four for the "Handful, or simply, Hand", but adds "The hand among horse-dealers, &c. is four-fingers' breadth, being the fist clenched, whereby the height of a horse is measured", thus equating "hand" with both the palm and the fist. Similarly, Wright's 1831 translation of Buffon mentions "A hand breadth (palmus), the breadth of the four fingers of the hand, or three inches", but the "Encyclopædia Perthensis" of 1816 gives under Palm (4): "A hand, or measure of lengths comprising three inches". Today the hand is used
Rack unit Rack unit A rack unit (abbreviated U or RU) is a unit of measure defined as . It is most frequently used as a measurement of the overall height of 19-inch and 23-inch rack frames, as well as the height of equipment that mounts in these frames, whereby the height of the frame or equipment is expressed as multiples of rack units. For example, a typical full-size rack cage is 42U high, while equipment is typically 1U, 2U, 3U, or 4U high. The rack unit size is based on a standard rack specification as defined in EIA-310. The Eurocard specifies