Abstract: The system comprises a shelf support arm (2) adapted to be mounted horizontally and a support bar (1) adapted to be disposed vertically and means for mounting the bar (1) to a vertical wall or other support surface, sliding means enabling the arm (2) to slide up and down the bar (1) and retaining means to secure the arm (2) to the bar (1) at any desired position. The arm (2) is a two sided member (9,9) with an external flange (3) at the end of each side (9) and the bar (1) has a profiled section that provides spaced apart and opposed recesses (8,8) to accommodate the flanges (3,3). The retaining means includes expandable means (4,5,6,7 and 10) held by the arm (2) and operable by actuating means (4,6,10) to urge the flanges (3,3) apart laterally and to engage the bar recesses (8,8) sufficiently to secure the arm (2) in a desired position.