Try Kay England's "Nifty Notions - half square and quarter square rulers." They make great HST and save on fabric, too. Best part is No Marking. You determine the best place for the bias edge and choose the ruler for that. Cut the strips 1/2 inch wider than you want the height of the block you use. One edge already has the point cut off and I have started using Martin Mitchels little corner cutting template to nip the other corner, which makes it easier to fit them together accurately.