More ideas from Igor
magnetic latch (invisible drawer lock) http://www.core77.com/blog/object_culture/simple_invisible_and_attractive_drawer_locking_system_21700.asp

"Touching the included magnetic key fob to the front surface of the drawer engages the magnet, allowing you to slide the unseen latch open and closed." / also a puzzle-box plot point in Angelmaker / concealed access go slow