A boom is a vertical scaffold pole with fixed horizontal boom arms onto which lanterns can be mounted to create side light or cross light across the stage.
Depending on the height and weight of the lanterns, the top of a boom may need to be hung from a rope attached to the grid at the top of the fly tower and mounted in a base that is screwed to the stage floor. A shorter boom with less weight on it may just be weighted at the base. A boom base consists of a flat metal plate with a short socket mounted on it into which the vertical boom is fitted. A bolt through the socket and boom ensures the safety of the boom. Weights are placed on the metal plate of the boom base to hold it in place.
A ‘tank trap‘ is the best boom base to use as it’s a heavy metal plate with a suitably long socket to keep the boom upright