A combination tray and wheeled cart (10) has three positions: an initial storage position with minimum space requirements; an intermediate carrying position configured as a conventional tray provided with an overhead handle for carrying to a job site, and a third erected operational position for mobile use on the job site. The combination tray and wheeled cart (10) is relatively lightweight, yet sturdy, and may be moved from one position into another position quickly and easily. Respective pairs of legs (20, 21) are pivotably mounted to the sides (12, 13) of a tray (11); and balls or casters (25) are provided on the ends of the individual legs (17). A shelf (27) is pivotably carried by one (21) pair of legs (17) and is releasably secured to the other (20) pair of legs (17), thereby structurally bracing the combination tray and wheeled cart (10) in its erected operational position. A variety of insert trays (39-44) adapt the combination tray and wheeled cart (10) for particular purposes.