Riggers are a breed of their own. Some specialise in wire effects and carry special equipment for all hanging effects. Others tackle basic set construction. When scenery reaches a certain size we use scaffolding to support it. It's again a very specialised trade as certain techniques require adhering to. Aluminium tube (as opposed to steel) is hired specifically for the job and a rigger often carries his own stock of equipment including special rollers/bearings etc. for moving sets effortlessly around the stage. Quite often scenery is strapped together on the floor and tubed up behind prior to moving into position. Riggers also hang most ceiling pieces and quite often work with the electricians rigging lights from the gantry.