I am attempting my very first patchwork quilt as a gift to a friend. I am following instructions in a book and so far everything has gone smoothly. That is until now. I have cut 11"x11" squares and am sewing the squares together with a 1/2" seam allowance. The rows are turning out nicely, until I laid them back down on the floor and realized that the intersections weren't lining up. Some line up, some are off by at the most 1/2". What do I do? When I sew the rows together the intersections need to line up just right or the quilt won't look right. Please help! :?