At Wal-Mart they have a June Tailor contraption "Perfect Half-Squar & Quarter-Square Triangles ($12.97). Along the sides (one side for marking and the other side for cutting). On the marking side you line the blue line up with the point and draw your lines in the slots on either side of the blue line. On the cutting side, you line the cutting slot up with the points and the dash lines up with your stitching. I just bought one and it works great, much better than those little narrow rulers.