Hollow spy bolts
Brian Dereu of Hollow Spy Coins showed us how to make this hollow dead-drop bolt for stashing secret messages back in MAKE 16. It’s not hard to do if you have access to the necessary equipment–a drill press, hacksaw, vise, grinder, and the appropriate taps and dies. But if you don’t have those tools, or you don’t have the time to use them, and you still want a spy bolt, Brian will gladly sell you one hand-made by his family and him for the not-unreasonable price of $37.