The Resident Evil 4 Remake small keys are items that you use to unlock drawers in the village and castle regions, giving you some extra treasure to sell and spend on your precious guns. Unlike the village's Wayshrines or the castle's Square Lock Boxes, small keys are only single use, meaning you have to locate more if you want to keep opening locked drawers.
One thing worth noting is that treasure in the castle understandably seems to be a lot better than treasure in the village, but Resident Evil 4 Remake does provide enough small keys to open every drawer you come across. Once you get to the island these keys are useless, so make sure you use them before you leave the castle. That said, here are all small key locations in Resident Evil 4 Remake so you can filch them for yourself.
