Shelf with secret compartment: insert a 6x3mm magnet into the hole and it will lock in place when closed. To open, use another magnet (see video). Simple and functional.

A 6x3mm magnet is needed.and a second magnet to open it.

There are two models: one with a 0.15mm tolerance and one with a 0.20mm tolerance. The 0.15mm model worked perfectly for me.