Diagonal Seam Half Square Triangle
This method starts with two slightly oversized fabric squares and creates two half square triangle (HST) blocks at a time – perfect for those times when you want accurate blocks and pointy points
Find the finished size of the HST patch. Add 1-inch to that dimension and cut two fabric squares that size.
Cut size = Finished size + 1-inch
Example: For finished size = 2 ½
Cut size = Finished size + 1-inch = 2 ½ + 1 = 3 ½. Cut 2.
Layer fabrics right sides together. Draw a diagonal line from corner to corner.
Sew a seam ¼-inch away from both sides of the drawn line. Cut on the drawn line.
Open block and press. You will have two blocks.
Line up the 45 angle line of your ruler on the diagonal seam and make sure the unfinished size of the patch is on the fabric (3-inch x 3-inch in our 2 ½-inch finished square example). Trim to size.
- Sew parallel to the drawn line from beginning to end of the seam
- Larger square ruler provides more stability during trimming. Grip dots on the ruler are also useful
- Bloc_Loc makes specialty rulers with a seam allowance groove for trimming HSTs. It is a uni-tasker tool which works really well