Dry-fitting a dowel joint is a must before you glue it together, but the dowels are made to such tight tolerances that they can get stuck in their holes. To prevent this problem, I sand pairs of dowels of different sizes down a few thousandths, then I.D. them with markers or dye to set them apart from the rest of my dowel supply. I save these marked sets for dry-fitting. They don’t get stuck, and once I know things fit properly, I switch to regular dowels for the final glue-up.