Slide rule, special purpose: builders, closed frame, single-sided, dual slides extending beyond the stock, wood with bevelled edges. Brown is colour. "G.Birks" written in bottom right corner on facing surface. On reverse/back surface "Makers G.T. Cooper & Sons Ltd, London. S.E. 9" is written in small black script.
Stock, upper: (blank)
Slide, upper: Half Beam in Feet (2 ½ - 60)
Stock, middle: Rise of Beam in inches (0 - 30)
Slide, lower: Width in Feet (0 - 100)
Stock, lower: Width in Feet (0 - 100)
on face: scale mnemonics, with "Half Beam in Feet"; "Rise of Beams in Inches"; "Width in Feet"; and "G.Birks" all written on rights side of facing surface.
on reverse: "Makers - G.T. Cooper & Sons Ltd - London, S.E 9."