Measure the length from your bed’s frame to the floor. There is usually about six to eight inches under each bed. Purchase drawers that are about four inches tall if you have six inches of room or drawers six inches tall if you have eight inches of room.
Turn the drawers over so the underside is facing upward. Drill four holes for each caster into the corner of the drawers.
Place the casters over the holes in the drawers and drill the screws into the holes to attach the casters to the drawers.
Turn the drawers over and slide them under the bed.