The red with the cream at a RIGHT ANGLE , has the ruler on top showing where you pencil in the sewing line. When you sew on the 45 degree angle mark, the dark and the light are opened out to form the pieced 8 inch strip. Once you open up the sewn strip, check to see that it is straight and if it looks good, cut away the extra triangle from the back. 5 of these pieced strips are sewn together to make a block.