Abstract: An expandable racking system for trays or the like having at least one upright member, at least one tray slide member, and an interlock member for slidably connecting at least one tray slide member to at least one upright member so that the alignment of at least one tray slide member relative to at least one upright member is correct and the height of at least one tray slide member relative to said at least one upright member is initially adjustable to suit user needs.