This past summer, our production of The Grand Duchess of Gerolstein at the Santa Fe Opera had a lot of tricks. Like… a lot of them. One trick I worked on was a set of magically-appearing flags. The set had seven flag poles along one wall, and during one big moment of pomp and circumstance, the design team wanted flags to suddenly appear on them. The idea is kind of like those “bang” flags that pop out of guns in the cartoons.
The basic mechanism behind the trick is that each flagpole has a second pole which sleeves inside. The two poles have slightly less than half of their surface notched out, as you can see in the photo above. The outer pole is fixed in place on the set, while the inner pole can spin around inside. So you can spin the inner pole to a position where the whole flag pole looks like a solid rod, and the flag is trapped inside. Then when you spin the inner pole around so the notches line up, the flag is free to drop down.
You can watch it all in action in the video below. The video also shows how I rigged the tubes so they could be activated by pulling a string off-stage, since there was no room on set to activate them directly.