NEWINGTON, Conn. -- On a recent evening in this quiet suburb, Matthew Fiddler hunched over a door lock, jiggling it with a pick and poking it with a wrench. In just a few moments, it popped open. Mr. Fiddler wasn't locked out and he isn't a thief. Instead, the 36-year-old father of four, clad in khakis and a blue button-down shirt, was seated around a table with a handful of people who pick locks for fun. The group, a chapter of Locksport International, gets together monthly to poke and prod everything from padlocks to dead-bolt cylinders. They swap tips, hold...