The Resident Evil 4 square lock boxes in the Castle section need a special key called a Cubic Device, and you won't be able to open them without it. It's definitely worth doing - those five square lock boxes spread around the Castle, and one of them actually contains a unique weapon that you can add to your pool of all the other Resident Evil 4 guns - the Assault Rifle. Clearly this is an important secondary objective among all the other ones you can work through in the Resident Evil 4 Remake, and with that in mind, we've laid out the locations for all the Resident Evil 4 square lock boxes and where you can get the cubic device to unlock them all. Pinhead would approve.
Resident Evil 4 square lock box and cube key locations
There are five square lock boxes in the Resident Evil 4 castle. You’ll find a couple of these lockboxes well before you get the cube key so be prepared to backtrack if you want to get all the treasures. Do note that you’ll also find a few of these boxes while playing as Ashley, but you’ll have to unlock them later as Leon. Here are the locations of the five Resident Evil 4 square lock boxes and the necessary cubic device key, as well as the rewards you get in each one:
All Resident Evil 4 square lock locations
- Audience Chamber: In the northwest corner of the chamber, you’ll spot the lock box in a barred cell, but there’s no gate so you can walk straight inside. You can collect a Justitia Statue from this box. Make sure you also collect the Resident Evil 4 Yellow Herb in the chamber if you haven’t already.
- Grand Hall: Head into the Merchant’s shop room and go to the corner near the fireplace. This square lock box holds a Butterfly Lamp. If you still need to unlock the previous lock box, use the other door in this room to reach the train that takes you directly back to the Audience Chamber.
- Cubic device near the Armory: After defeating the parasite knight armor, you can escape the Armory and head back to the Grand Hall via a new corridor. As you head down this corridor, you’ll spot a chest that can be opened to reveal the cubic device you need to open square lock boxes. You can now backtrack to the previous lock boxes to unlock those.
- Library: Go up the secret staircase that you will have activated as Ashley at the south end of the Library. The lock box is embedded in the wall and holds the CQBR Assault Rifle.
- Salazar Insignia puzzle room: Upstairs from the Library, you’ll get into the room where Ashley places the Salazar Insignia to free Leon from the Grand Hall cage. The lock box is to the left of the insignia slot and offers a Golden Lynx.
- Throne Room: Head to the southeast corner of the Throne Room to get the final Resident Evil 4 square lock box. Unlock it with the cubic device to get a Resident Evil 4 Gold Chicken Egg.
How to use the Resident Evil 4 cube key to unlock square lock boxes
Now that you know where to find all the square lock boxes and you’ve presumably got the cubic device key, you can start unlocking each box. All you need to do is select the cubic device when interacting with the square lock box, and then orient the cubic device so that its shaped grooves match the teeth on the box. When it’s in the correct position, press confirm and the cube will slide in to unlock the box.
Make sure you open all the square lock boxes before you ascend the Clock Tower in Chapter 12, as there is no going back after this point. Although, once you have got past Chapter 12, you can safely sell the cubic device to the Merchant, as there is no need for it anymore once you reach the island. Here you’ll need to focus on upgrading a Resident Evil 4 keycard and must find the Resident Evil 4 wrench too.
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