Most people probably haven't seen this month's item before. That's because it's not meant to be purchased by the general public. If you've ever wondered what the hole in the elevator door is for, this is it. Specifically, it's used to release the doors for maintenance or in an emergency. After sliding the rod in the hole, the links drop down the interior, creating a 90-degree angle. When it's turned, the links move up the door, tripping the mechanism that releases the doors. To see the links bent, click here.

You're not likely to run across these keys at a flea market. They're used mostly by people in the elevator industry, elevator maintenance workers, and fire and rescue personnel. Nevertheless, they are out there, although many manufacturers have progressed to a single link on the end. To check out another variation, click here. To enlarge the pic above, click here.