Abstract: A releasable caster for use with a moveable structure having a bottom wall wherein the caster has a swivel connected yoke and stem with the yoke supporting a plastic wheel. The stem includes a manually operable spring biased rod that has an indentation between its ends and co-acts with a ball detent. A shell with a flange at its outer end is adapted to be received in an opening in the wall. The shell has an abutment, prefereably in the form of a groove with the upper edge forming an abutment which copperatively locks the ball detent or releases the ball when the rod is moved longitudinally or rotationally.