I have 5 yards of solid black wool and would like to begin making a kilt from it. However, the top and ends of this wool are not straight, but the selvage is. What I need to do first is start marking lines for sewing/pleating, but I can't do this because I don't have a t-square or protractor, though I do have a rule and tape measure. Can anyone here walk me through building a 90 degree angle so that I can cut the ends off straight? From there I can easily measure/chalk for the pleats.