In the movie, who put the poster back up on the wall after he made his escape?
If you mean before his escape was discovered, he did. He hid behind it while digging the tunnel; there was a flashback scene showing that.
Weird. I could have sworn that, in the final scene with the warden, the poster was solidly fastened to the wall and not just hanging down.
You can’t tell,
I think we’re left to assume that the poster was attached to the wall at its bottom as needed.
That’s not the big issue. In an old drafty building like that, with innumerable unsealed ducts and passages and mismatched sections of wall, that poster will be constantly “breathing” and making a crinkly noise while doing so, and likely even before he breaks through into an old dusty anteroom. Recall the anteroom in question also has windows (for Andy to see the thunderstrikes), only one of which needs to be less than 100% perfectly sealed, and during a storm the poster will move even more.
Maybe that is why I assumed the poster was secured to the wall, and not just hanging loosely.
He’s smart. He probably figured out a way to get it tacked down from inside before his final departure.
And he could have had a sheet attached to the walls of the tunnel behind the poster to reduce any air movement against the back of the poster.
When the warden throws the rock at the poster, the way it neatly punches a hole without the paper rippling at all seems like it would require the poster to be firmly attached all around the perimeter. (Similarly when he puts his arm through the poster.) I think we have to accept that the poster was attached to the wall using Dramatic License brand adhesive mounts.
Now do Moonrise Kingdom!