I'll give it another attempt before pictures. When sewing the top piece to the bottom: say.. having sewn 1/2" squares together in a strip and attaching them to the bottom fabric, the way the Baby Lock Grace's 1/4 pressure foot is designed part of the pressure foot (the left side) hooks or catches under the 1/4 seam on that top seam of the half square as I sew the top to the bottom in a strip. Does that help explain?