[other traps]

Under Glass

With most of our traps, half the challenge is finding the trigger before you accidentally set it off. This trap goes the other direction: sliding back the box lid reveals a snugly-fitting glass dome, under which sit two armed poppers (called Bingo Shooting Devices in the novelty biz). The trap's workings are fully visible and it's perfectly safe so long as the glass dome is kept in place, but because the dome is a nearly perfect fit for the box it's nearly impossible to remove the lid far enough to allow access the poppers without them going off first.

When people ask me how to disarm a trap I'm giving Jay I'll often joke that "I just design them, disarming them is his problem," but in reality I like to know that I can get through it before I hand it off to Jay. This one almost had me stumped, because there isn't enough room for the usual tricks of the trade to work. In the end I discovered two different techniques to disarm this style trap, though I confess at the last minute I made a minor design change that made it even more difficult than the version I had disarmed.


The key to this trap is finding the right combination of box and glass dome such that the dome fits perfectly into the box. I found both at thrift stores over a period of a few months: the box was a wooden one with a round hole designed to hold drink coasters, the dome is a round glass bowl designed to be an ashtray or small candy bowl.


There are lots of variations you can try with this trap design. You can use one or multiple poppers, attach the poppers to the inside of the box or to the dome itself, stack several poppers together, allow the poppers to move freely or tape them down, and so forth. Different designs will make the trap harder or easier to disarm (and for that matter, to set), and your choice of box and dome will also constrain your design.

For my initial design I had a single popper taped to the underside of the dome, and covered the felt bottom of the box with a cut-down playing card so the popper wouldn't catch and twist when the dome was rotated. The trap worked well, but I was having trouble with some of my caps being duds. For my final design I used two poppers instead of one to insure against duds, and attached them to the playing card itself rather than to the dome because I liked the aesthetics better.



Single popper attached to dome

Two poppers attached to card


Arming consists of setting and loading the popper(s) and then holding them down with a strip of stiff paper or cardboard while lowering the dome. Once the dome is in place, you can slide the cardboard out through the side. (If only disarming was that easy!)

For a more dramatic effect, you can sandwich a small sheet of flash paper between the cap and the firing pin. The paper will be held in place by the cap, and will be set off by the cap. The bang will be a bit more muffled than with just the cap, but with more fire.


Placing dome over cardboard


Arming Video (Quicktime, 2.1M)


There are several potential methods to disarm this kind of trap, though depending on the particular trap implementation some of them may be more or less effective. I've only actually used the first two methods, the others are suggestions I've heard that sound plausible but haven't been field-tested. Note that there are various destructive methods you could use to open this trap without setting it off, such as drilling a hole from the underside, but that's considered cheating: the idea is to get the "treasure" out of the box without setting off the trap and without damaging either the box or trap itself.