Save time with Sew Straight by sewing unmarked diagonal lines as Snowball or Triangle Squares. Accurately sew bias seams for Binding in a jiffy! Sew perfect 1/4in seams! There are countless ways to use Sew Straight! No Key Needed. Sewing on Unmarked Diagonal Line. Sewing Miter. Sewing Accurate 1/4in Seams. Sewing Bias Seams for Binding. Sewing Diagonal Lines for Pieced Squares.