Assembled the new frame, added casters. The old frame already had casters. Removed desktop, set it aside, rolled old frame out, rolled new frame in, adjusted length, attached desktop, mounted control units, tested, worked fine the first time. The old frame worked fine, too, but after adding casters, it wouldn't go low enough. This frame solved that problem. Adding casters was a snap. Removed leveling pads, screwed casters in. Uses M8 screw threads.