Hello, I only draw 1 line down the center of the lighter fabric...then I put the little lip of the quarter inch foot on the line stitch with the lip following the line....sew off the fabric a little turn the fabric the other direction letting the lip follow the line again and its stitched 1/4 inch from the drawn line on both sides of the lines.....then I cut fabric on the drawn line and you have 2 half square triangles...I also orginially cut the squares 7/8 inch larger than needed....that way after you cut on the drawn line and press....use the 6 1/2 square ruler and put the line down the center diagonial and square up the block to the size needed...