Bonnie Hunter has a video and shows how she matches up the tumbler. Basically just find the center. Later you will be cutting the tails. No big deal She uses the Dresden 8 1/2" tool to make hers. Jenny Doan has a tumbler template and pretty much the same on a video. Not difficult. I like the idea of not having to buy an expensive template/ruler. Fons and Porter had a video using a tumbler template/ruler that shows a square edge to be "nicked' off to better align.