Cut ten 2 7/8 inch squares from a white-on-white fabric.
Cut two 4 7/8 inch squares from a white-on-white fabric.
Cut five 2 7/8 inch squares from a light blue fabric.
Cut five 2 7/8 inch squares from a dark blue fabric.
Cut one 4 7/8 inch square from the light blue fabric.
Cut one 4 7/8 inch square from the dark blue fabric.
Cut all of the 2 7/8 and 4 7/8 inch squares on the diagonal to form triangles. Sew a blue triangle to each white triangle to form twenty 2 1/2 inch squares and four 4 1/2 inch squares.
. . . or place a blue square on each white-on-white square and draw a line across the diagonal. Sew 1/4 inch from each side of the line, then cut on the line and press open.
Prepare four 6 1/2 inch blocks as shown -- two with the light blue and two with the dark blue.
Assemble the block as pictured; you will have four 6 1/2 inch blocks that should be placed as illustrated in the graphic.
Your finished (unfinished) block should measure twelve and one-half inches. Be sure to leave the seam allowance on the block, DO NOT cut it to the 12 inch finished size -- as the “finished” measurement represents the block size after it is sewn into a quilt top.