A square ruler with engraved markings on one side and diamond shaped holes.  The ruler is used to measure quilt fabric for cutting to the desired size (squaring up the quilt blocks).  

The diamonds provide visibility of the fabric through the holes.  The points of the diamonds are on ½" intervals and the bends in the diamonds provide 1/8" intervals.

There is a groove on the other side that is used to slide the ruler along the half square seam to position the square for cutting.

I printed with the engraved markings down, to avoid the need for supports for the groove.

After printing I used a black marker to make the numerals more visible.