The WonderCut Ruler utilizes a wonderful technique for making a lot of half-square triangle blocks very quickly.
The WonderCut Triangle Ruler uses the "wonder" technique to quickly create equilateral triangles. These rulers are completely self-contained tool for cutting strips and triangle blocks.
From the Manufacturer's Website:
"The Wonder Cut Ruler is the ultimate ruler to use when making half-square triangles , or three-part squares, or even four-part squares perfect every time! No paper to peel, no fabric points to get stuck in the feed dogs of your sewing machine, and best of all, no math to fuss with. The Wonder Cut Ruler has all the math included in its exclusive design. If you can sew a 1/4" seam, you can make a perfect half-square triangle every time. Did I mention the Wonder Cut Ruler was fast? We knew using the ruler made making half-square triangles fast, but just how fast is fast? Try 130 in an hour from fabric on the bolt, to half-squares pressed open. We believe that no other ruler on the market can make that claim."