Scale: 1:1. A model depicting a section of a girder, or beam, part of the frame of a vessel. Made entirely from an unknown metal, it shows a cross section of the girder, one end with a flat t-shaped shoulder gradually tapering down into a narrower section which is then parallel and into a rounded bulbous end. The side of the section are painted black. One face of the section at the top is stamped "Butterley patent".

One of a set of three models. This model is a larger section then the other two in the set: see SLR2320 and SLR2321.