I have this ruler and have never taken it out of the package. I did to look at the instructions and what the ???. It says Join fabric shapes sewing with 1/4" seam allowance, to create quilt top. LOL
On the back of the package the picture of the four quilt blocks may be an indication. Looks like each block was sewn in two pieces then the two pieces sewn together to make the block. It take four blocks to make the one block.