A dolly (10) for supporting a tank (12) standing on an end is provided with a T-shaped plastic base formed by a crossarm (21) and leg (22) that are joined by an adjustable interlocking connection (38, 62). Both ends of the crossarm (21) and the end of the leg (22) remote from the crossarm (21) are provided with arcuate grooves (41) that receive the bead (18) surrounding the bottom of the tank (12). The heads (44) of fastening screws (43) extend over the grooves (41) to retain the bead (18) therein. A metal axle rod (23) extends through a longitudinal passage (65) in the crossarm (21). This passage (65) has an open top in the region between the grooves (41) in the crossarm (21) so that a tank (12) on the base (20) engages the rod (23) to be supported directly thereby.