I have a folding kitchen cart with shelves and wheels for my cutting table. I drilled holes on the back/long side and then put small bolts through to hold my rulers. I did put on the nuts to keep the rulers in place.
At a quilting retreat we were each given a hanging ruler holder. It is made of fabric with a top loop to hang it on something. This is hanging on one of the above bolts.
I also use those ring style belt holders. The ring is just right for putting on my specialized rulers. Those are hanging from the side of the bookcase in my 'studio.'
Wall space is at a premium in my place. There isn't room for a stand alone ruler holder either.
Guess you find what you like that fits your space.
ali