I needed a reliable way to make relative measurements to set the height of the rails on my mpcnc and to set the horizontal axis on my 3d printer. Using both the bubble level and the measurements marked on the scale you can get surprisingly accurate relative measurements. Using the locking screw you can also lock the height and transfer measurements I used it to hold my mpcnc rails in place while tightening the fixings This thing has been designed to accept a standard 1" wide adjustable square,