No, you don't have to have this ruler. I attached binding for years with no ruler. I also attached binding for a couple more years with someone else's ruler. But if I have the choice to use nothing, use the other ruler, or search thru my studio for this one, I will stop what I'm doing to find this ruler! Includes lines for 1/4" and 3/8" seams.
003 - Wheatridge Studios 90 Degree Binding Ruler