I know that others can cut perfect HSTs with their regular ruler, but not me! I really agree with the bloc loc ruler solution. They are pricey, but worth every penny. The channel makes it easy to position, it doesn't slip and as you mentioned, keeps it from rocking. While you can get away with the 6.5 inch size, and cut that size & anything smaller, I've been buying the other sizes as needed for specific projects. If I have to cut 100 HST for a project it's worth it to me to have the right size Bloc Loc ruler and my rotating mat. The job goes quickly and the accuracy is wonderful. I think the only place that sells all the sizes is the manufacturer, so no 40% off!