A unique idea to measure angles accurately. As you can see in my picture, the tool fits over your band and displays the exact measurement in a small window. Whatever your window shows, add 1 inch; So in my picture it shows 9 and 7/8 inches. Note that the tail expands 1 inch, so the tail size is a 10 and 7/8. It includes a bubble level so you can keep your measurements level. The Stanley Fatmax might not fit here, but my Lufkin works fine. So if you are trying to measure 8'9 1/4" from the wall set the measurement on the tool and then place the tool at the corner and where the hook ends on your tape which is 8' 10 1/4" equals. . Inches So you set the tool up 1 inch less than you want to measure.