Assemble Pinwheel Units
1. Use a pencil to mark a diagonal line on wrong side of each red print 3-7/8" square.
2. Layer a marked red print square atop a dark blue print 3-7/8" square. Sew together with two seams, stitching 1/4" on each side of drawn line (Diagram 16). Cut pair apart on drawn line to make two triangle units. Open each triangle unit and press seams toward dark blue print to make two triangle-squares. Each triangle-square should be 3-1/2" square including seam allowances. Repeat to make 16 triangle-squares total.
3. Sew together four triangle-squares in pairs (Diagram 17; note color placement). Press seams in opposite directions. Join pairs to make Pinwheel Unit A. Press seam in one direction. The unit should be 6-1/2" square including seam allowances. Repeat to make a second Pinwheel Unit A.
4. Referring to Diagram 18 for color placement, repeat Step 3 to make two of Pinwheel Unit B.