Locks and Security (2005)
mattblaze.org
mattblaze.org
A couple years back, I built a custom jewelry box for a customer who supplied a Bramah box lock for the job.
Locks for boxes are a perpetual source of hassle in sourcing. The thing to realize about a box lock is that rather than preventing a shearing motion along the key way axis (like a door or drawer lock), they instead prevent you from making a pulling motion away from the keyway axis. This is comparatively uncommon (apart from patio doors, which are not furniture-sized and are rarely nice).
As a consequence, your options for a box lock are limited. Basically everything that's actually available on the market apart from Bramah is a warded lock. They are not particularly secure, though you can get nicely enough made ones.
Box locks are typically half-mortise, meaning you can see the back of the lock from the inside of the box. If that doesn't make sense, consider a standard door lock. Those are full-mortise, meaning that the body of the lock is entirely contained by wood on both sides of the door.
When you install half-mortise lock, you cut the mortise for the lock body, fit the lock into the mortise from the back, and give it a little bump to make an impression for where the pin the key fits over goes. Then you can drill through from the back side, cut out the keyhole, and usually also fit an escutcheon over (or into depending on the type of the escutcheon) the key hole. They key thing here is that you can get your lock nicely fitted and flush in its mortise and then drill the hole last. You have opportunities to double-check and adjust the fitment of the lock as you go before drilling through to the show surface.
With a Bramah, everything is backwards. You drill a hole from the show surface for the cylinder, and then you mark out and cut the mortise afterwards. If you've left the top of the lock a hair proud of the surface of the box, you're shit out of luck. You get one shot to drill that hole and drill it perfectly or you've spoiled the show surface. Usually after considerable effort to get to the point where you're ready to install a lock. Among other things, you've typically gotten to the point where you have hinges installed. Which in turn means the whole box is together.
It goes without saying that a test installation or two is highly recommended.
The paper is really good, and worth a read, even though it is from 2003:
There are master keyed systems that don't have that combinatoric weakness. Here's the Lock Picking Lawyer disassembling a prison lock where there's a separate "master ring" for the master key. So combining settings from the master key and the operating key will not open the lock.
This lock was opened with a wave rake, though, so it's not very good.