I use fabric dryer sheets after they come out of the dryer as some of my foundation for string blocks. They do make rectangular blocks rather than squares. For 2 different quilts I used these in the following manner: I sewed the blocks into long strips, trimmed them evenly, then cut in half. Now I had twice as many long strips about 3" wide, which I used as borders for the quilts, which were scrappy. Bonus borders! They use up scraps & are great for when I need mindless sewing.