Anna from Plan B updated an old ball cap with a panel of square metal studs. Rather than setting the studs directly into the cap, she created a studded panel that she glued to the cap. She did it this way so she could be sure the studs were set in straight lines. This would also be a good solution for adding studs to bags, jackets, etc. in places where it’s not easy to reach inside to set the stud. Go to her blog to see how she makes the panel.
[photo from Plan B]