I'm making a quilt, a star pattern. The instructions require me to purchase a 41/2" triangle ruler....really??? Do I really need to do that? I tried making one block using my regular reqtangular ruler and it worked ok but took many steps to figure where to cut. When they say 4 1/2" are they talking about the horizontal, vertical, or angular measurement? Or from the point straight accross to the edge? I really don't want to buy another ruler when they ask for the one I happen to not have.