Abstract: An apparatus for limiting deviation of an endless belt/belt sleeve from a desired rotational path. The apparatus has first and second rollers each having a rotational axis and cooperatively supporting an endless belt/belt sleeve trained therearound for rotational movement in a predetermined path. A first member is mounted on one of the first and second rollers for movement axially relative to the one of the first and second rollers. A blocking structure defines a shoulder for engagement with an edge of an endless belt/belt sleeve trained around the first and second rollers to limit movement of an endless belt trained around the first and second rollers in a first axial direction relative to the one of the first and second rollers.