The keys have different openings in them.

There are keyholes on the sides of the box. The keys should be put in the relevant keyholes (Note: you shouldn’t turn the key, you only have to insert it). The number of the openings in the key should match the number of the semicircular recesses next to the keyhole.

When all keys are placed in the appropriate order, a hidden slider on the front of the box will be pushed out. Sometimes it is not necessary to put the fifth key into the keyhole, when the box is held horizontally.