Im chilling the cookie dough, now (first batch). thought it would be easy to figure out 1/4 thickness...and Its not! I have only a rolling pin. This is my first time making cookies from scratch, so I didnt check into the doodads for rolling out the dough. How can I determine 1/4 thickness without having dowels or rings, with only a rolling pin. I need to make 3 more batches and want them consistant to each other in size.