Aspects of the disclosure relate generally to rack systems for housing computing devices. The rack may include shelves supported by flanges of a pair of corresponding inserts. The flanges may be spaced along the length of each of the inserts. The distance between the flanges may define the height of a shelf when placed in the rack. The pair of corresponding inserts may be placed along an inner sidewall of the rack by mating hooks of the inserts with corresponding slots of the inner sidewall and subsequently removed by demating the hooks and slots. For example, a pair of inserts with one distance between the flanges may be replaced by a pair of inserts with another distance between the flanges in order to increase the shelf height of the rack. By replacing the shelves and/or the inserts, a user may quickly and easily in order to reconfigure the rack.