Ball cap storage with towel bars and curtain clips.
Ball Cap Storage Use an old curtain rod & curtain ring/clips to store hats
On closet door back
13 Storage Ideas to Save Your Space
This is how I organized my son's hat collection. All items are from IKEA and the total cost was around $15 to hang 50 hats.
one of the simple solutions for hat storage
Another hanger-plus-rings hack, this solution allows baseball caps to nest within each other so they take up less space. But hanging them horizontally means you can still see exactly what you won. See more at House Dressing Style
ball cap storage
A cap storage idea from New Era fan Chris K.