I like to use the Bloc-Loc rulers when doing HST/flying geese/log cabin etc that they have rulers for. For squaring up regular blocks that I can't use the Bloc-Loc rulers for because they contain a mixture of blocks and I can't use the ledge to line them up, I use the
Lori Holt Trim It Rulers Trim It Rulers Lori Holt for Riley Blake Designs - Bee In My Bonnet. I like to have the size of my block. Just center it on with the ruler markings and trim. They also have rectangle sizes as well.