You see a loose board.
Location
Tom's barn, here, Darashia's Bath of Dreams, here, the Necromant House on the Plains of Havoc, here, and Mac Noodles, here.
Notes
This board has gotten loose at some point in time.
You can use the one on Rookgaard to get a Doublet (Doublet Quest), the one on Darashia to get a Piece of a Broken Amulet (Mouth) (Koshei the Deathless Quest), the one on the Plains of Havoc to get Key 3701, and the one at Mac Noodles to get The Lower Right Part of a Map (Treasure Hunt Quest).