I believe this ruler creates the same block as the Tri recs rulers. It can be a difficult block to make because of the angles. Not horrible, you just have to be careful. You could do them as paper pieced. Then the blocks come out spot on. Another thing I have done is make the block slightly bigger and cut it down. You just have to be sure to have the 1/4 inch seam allowance at the top so the triangle point is not cut off.