Design sketch for a box spanner made from bar with a broached hexagon.
| Identifier | WestWitteringFiles\B\June1918\ Scan0 | |
| Date | 13th June 1918 guessed | |
| BOX SPANNERS MADE FROM BAR & HEXAGONS FORMED BY BROACHING HEXAGON CAN BE STRENGTHENED IF REQD. AT TOMMY BAR HOLES.. | ||
From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).