A 3 stud long beam with a large M8x1.00 fine pitch threaded hole in the middle. This allows beams to be connected to M8x1.00 screws or allows beams to move up and down a M8x1.00 threaded bar like a lead screw. There is also a grub screw on the beam so it can be fixed in position to the M8 threaded screw/bar.