Abstract: A rotatable roller assembly includes a roller, a housing, a support pivotably connected at one end to the housing for pivotal movement between a first retracted position and a second extended position, the roller being rotatably connected to the other end of the support, first and second notches defined in the support for establishing the first and second positions, respectively, and a locking mechanism slideably movable into and out of locking engagement with the first and second notches to effect releasable locking of the support and thus the roller in the first and second positions, respectively.