i learned this at a class years ago from Johanna Wilson of Plum Creek Quilts. When cutting down a HST ALWAYS line up the 45 degree line with your ruler and trim from both sides thus you will not lose your points. Thanks Johanna where ever you are. She had a cute sampler quilt called "Laura Engals Wilder Sampler" after all Johanna use to live on the banks of Plum Creed in Wisc.