Corner Triangle

Midpoint Triangle Join

Triangle-to-Edge Join

Attach a regular triangle to a square or rectangle edge by matching center points first, then sewing a standard 1/4 inch seam.

1. Fold the base edge (square or rectangle side) in half and finger-press to mark its midpoint.
2. Fold the triangle along its base to mark the midpoint of the long edge.
3. Place triangle and base right sides together, align midpoint marks first, then align both corners and pin.
4. Sew with a regular 1/4 inch seam from one end to the other without stretching either edge.
5. Press the triangle away from the base and trim dog ears if needed before adding the next seam.

Pro tip: Pinning the midpoint first prevents the triangle point from drifting left or right; this is the key to keeping points centered across repeated units.