Here is a quick tip for tracing patterns on glass. I usually print my patterns on card stock. When I trace them onto glass, they can be tricky to hold down and keep from sliding. I started using my favorite scoring stick to hold down the pattern while I trace it. It has a bit of weight to it and a rubber back. I bought my score stick years ago at a Glass Expo. I have a 12 inch and a 24 inch one. Creative Ceramics and Glass sells one that looks identical. Any ruler should work though.