The instrument consists of an aluminium base plate upon which is engraved an outline diagram of the ship and its compartments. The plate is set in a heavy brass frame and can be balanced on suspension points in a fore-and-aft, or athwartshps direction. A mechanical calculating device is fitted to the upper part of the frame and this includes various scales for calculating the ship's stability and trim.
The instrument is housed in a mahogany case which contains two drawers for storing weights.