When you activate the "Save and Quit" feature, the game will save a record of the items currently in your inventory and in the safe. If you do so after clearing out a room (but before triggering the next checkpoint), you can then load from your last auto-save and you will be able to clear the same room again, even though the available items will have already made it to your inventory. In this manner, you can collect those same items repeatedly. This trick can be exploited as often as you like in certain locations throughout the game, including near the first usable bench in Chapter 3, and then in the same room later in Chapter 4.