Rack shelf provides support for non-rackmount equipment such as consumer electronics, computers, power supplies, and chassis-style components. This versatile, three-piece shelf has width-adjustable side supports for expansion from 17.5 to 22-inch wide to provide extra mounting width behind the rails for larger chassis. In addition, the side supports can be installed with either the long or short side up to emulate the height of a 2U or 3U shelf without using front mounting rail space. The center section is precision formed from 16-gauge steel, side supports are formed from sturdy 14-gauge steel.