For my son's baseball hat collection I mounted a curtain rod at the top of his closet door. From it I hung the baseball hats, using metal shower curtain rings. (through the part in the back where you adjust the hat size). It is now a one-of-a-kind "valance", and is a neat way to keep the hats and still be able to see them.
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I put up the clear plastic hook/hangers (the ones that you can get off without ruining paint) in a neat row on my son's bedroom wall. He proudly displays all his hats, while being able to easily see them, and grab whichever one he is wearing that day.
I used small brad nails to hang my husband's ball caps. I hung them spaced around the ceiling of the den and bedroom, when he got to have so many.
