The preferred embodiment of the collapsible dolly of the present invention can be used for example as part of an overall moving system for moving a heavy, bulky load up a series of stairs which, as shown in FIGS. 1 and 2, includes primarily a stair climber basic tractor unit 9 with a special slotted loading platform 8 attached thereto, a load sled base unit 1', similar to that disclosed in the pri