To handle oversize sheets, the tympan is oversize. The frame, built with angle iron, extends from the bed at angles. When the bolts are tightened, it becomes rigid. The holes underneath the four washers are oversize to allow for height adjustment. Hinges are salvage. The counterbalance came out of a torpedo, it is classified. As the near side of the tympan is lifted, the counterbalance raises the far side. This minimizes twisting and slurring.