Making Half Square Triangle Units
There are several ways to make half square triangle units -- sometimes called triangles squares. Cutting and piecing individual triangles is perhaps the slowest and least accurate method. Quick piecing is a good choice because it helps you put these popular quilting units together quickly and accurately.
Triangle Squares from Squares
I like to make half square triangles from sandwiched squares of fabric that are sewn together twice along their diagonal, then cut apart to yield two units.
- Cut two 4-7/8" dark squares and two 4-7/8" light squares.
- Follow my easy instructions to make four half-square triangle units from the squares. When complete, the units should measure 4-1/2" square.
I nearly always begin with oversized squares, then trim my sewn units back to the correct size with a square ruler that has a 45-degree line along its center to help me ensure that each triangle takes up exactly half of a square's space (instructions are included in the linked tutorial).
Triangle Squares on a Grid
Use the long grid method to make four half square triangle units. Your fabric strip should be 4-7/8" wide.
Assemble the Pinwheel Block
Use Quarter Inch Seams Throughout
- Arrange the completed 4-1/2" half square triangle units into two rows as shown above. Press seam allowances towards the darker triangles.
- Sew the rows together, matching edges and midpoints carefully. Press the new seam allowance either direction.
- Check your block. It should measure 8-1/2" square. If your block is a slightly different size, read the Block Lotto Guidelines to determine if it is within the acceptable range.
- Repeat to make additional blocks. Be sure to use a different combination of fabrics for all blocks. Read the guidelines for exact guidelines.
