- Align strips for your triangle square units, right sides together and all edges matched. Pin the strips together along their length to keep them from moving apart.
If you are using a paper grid, align it with the matched strips and pin it securely in place. Pin through each square to keep edges from shifting as you sew.
- Begin sewing at one end, placing your seams a scant 1/4" from the diagonal line that connects squares. Use your 1/4" presser foot to gauge the distance or sew on marked seam lines. Stop sewing and turn at each corner to change directions.
- Remove the unit from the machine and repeat to sew a seam a scant 1/4" on the opposite side of the original diagonal lines.
- Use a rotary cutter and ruler to cut units apart on vertical lines. use a rotary cutter and ruler or sharp pair of scissors to cut each square into triangles along the center diagonal. Remove papers if necessary.
- Place the units on the ironing board, darkest triangle up. Place a warmed iron on top of each to set the seam. Press open carefully.
- Measure units with a square ruler to verify size. The ruler's 45-degree line should flow precisely along the line created by the unit's two triangles.
- Use the ruler to cut each unit back to its correct size if you constructed the triangle squares from oversized strips of fabric.