Abstract: Field-adjustable rack systems for mounting communications equipment are disclosed, including an adjustable communications equipment rack where the rack is adjustable from a floor mounted configuration to a wall mounted configuration, and the overall width of the rack may be varied by adjusting the base and the top in a plurality of different configurations. Also, height adjustment to the communications equipment rack is disclosed where the height of the rack may be adjusted without removal of the existing mounted equipment from the rack. Height adjustments are made by coupling a plurality of extensions to the vertical side rails of the rack, to arrive at the rack height desired. Methods are described for field adjusting communications equipment racks into various configurations, including floor mounted configurations and wall mounted configurations in a plurality of widths and heights.