Put razor blades in the right pockets and frequent the place to set them up.
I knew a guy once who lived in kind of a rough neighborhood.
He kept having stereos stolen out of his car.
The next time he replaced one he first tack welded six razor blades to the underside.
He awoke one morning to find his car door open and a pool of blood on the floor with a blood trail leading down the driveway. Stereo still intact.