I want to put a poster on the sliding door of my closet, but the doors are metallic, so I can't really punch holes in them.
Also, it goes behind the other door when it slides, so the system holding it cannot be much thicker than the poster itself or the other door won't be able to slide in front of it.
Ideally, it needs to be held as flat as possible and with as little spacing between the poster and the door, as sagging could cause the poster to be torn when the other door slides back and forth in front of the poster.
Best Answer
If it would work use magnetics. For supper flat use scotch tape, and tape the corners, or you could use poster adhesive strip but that will rase the edges a little.