first don't cut them into triangle yet. cut squares first then draw diagonally / once, right sides together and sew 1/4" down both sides then cut on drawn line and press open. if squared up it is to be a 2 1/2 inches the cut both fabrics into 2 7/8". you get 2 1/2 square triangles. hold your thread as you begin. learned the hard way, and ripped a bunch up.