Install a door without needing a second person to hold it upright or leaning it against a wall. These dollies allow you to wheel a door into place and align it with the hinges on the frame. Turn the knobs on the casters to adjust the height. Apply the brakes to prevent them from rolling away. Dollies hold 1 _3/4” thick doors; use spacers to hold 1 _3/8” thick doors.