Scale: Unknown. A working model showing the plan for increasing the leverage for operating a ship's tiller onboard a screw ship. The tiller mechanism, which is largely cast and made in brass, is fixed to a rectangular soft wood back board which is stained and polished, and complete with a stained mahogany frame. The mechanism consists of two tillers, fitted with a segment of a tooth wheel at one end and a hole at the other end, which would have been attached to the steering wheel via a form of cable or rigging. There are also two large toothed wheels either side of a smaller toothed wheel which ones assumes is directly connection to the head of the rudder stock. There are two angled thin pieces of wood batten fixed to the backboard on which the brass tillers would rest and operate.

In the middle of the backboard just below the tiller mechanism is inscribed a centre line, around which is a large and small rectangular box, with a hand written ink inscription "Aperture". The backboard is inscribed "Plan for increasing Leverage of the tiller in Screw Ships, By, Benjn, Bennett, Carpr., R.N. HMS Hulk Bellerophon Portsmouth."