EBay, Collectors, Flea Market & Antiques

Glass out of the bottom rail and the slide the glass out past the lock. I suggest putting a sliding lock at the very bottom of the glass. This makes it harder to pull out the glass past the lock. In the other bottom corner, screw a piece on the cabinet that blocks that corner of the glass from being pulled out.

We also had a guy either pick a few locks or had a master key. He was a tall older man of mixed race. Used a cane and had a short gray beard. To foil this, use 2 sliding locks of different makes. If you google "show case locks" you can find hard to pick locks.

Home Depo sells a stick on glass alarm for $9.