You are better off just putting an aim spot on the paper. Then take a price of cardboard and cut out a circle of the size say 16 or 24 and hold it over the pattern. You never center you pattern, in the perfect middle of the paper. This way you get the information you need more precisely by adjusting your cutout over the real pattern. Use a couple pieces of duct tape to hold the cutout in place and step back a few feet to gain perspective. A phone photo gives you a lasting record for later review. Write down shell information along with gun, barrel and date for your records. Patterns loose their information value if you cant tell one from another later.
Ive used paper, cardboard and a pattern plate like Stan was referring to earlier. Each works well but wind does not bother the plate at all where it does make changing paper a challenge sometimes. And you can shoot a lot of patterns quickly if all you have to do is reapply your paint surface. But use what youve got. Just patterning you gun puts you ahead of 90% of shooters who never do it at all. Just like people who check powder drops with scales are a small percentage of reloaders in shotshells.
