I can't really help you with the ruler question. But - there is a Jenny Doan (Missouri Star Quilt Company) tutorial that is great. She used two charm squares, right sides together. Sew 1/4" all the way around the edge of the square. Cut twice on the diagonal and you have 4 HST's. Not sure if I can link it, so just google MSQC fast and easy pinwheel tutorial and that should bring it up for you. There are so many great blocks you can make using HST's!