In our domain of concern, truss generally refers to a metal frame used to hang light fixtures from. It generally comes in three main designs – flat, box, and tri – which describe the shape created by the frame. By virtue of their construction trusses are very strong and able to carry extremely heavy loads. Most truss is now made of aluminum for weight reasons and sections can be bolted together to produce long pieces. Used extensively in concert production to form the ‘roof’ over the stage from which to hang everything from lighting to speakers. Even followspots can be mounted together with their operators who access their seats via circus style rope or wire ladders.