| Name and Model Number | Routledge’s rule |
| Country of Origin | UK |
| Date of Manufacture | c1805 |
| Front Scales | Routledge engineering (Soho) scales: D = 1 - 10 |
| Back Scales | Gauge points, conversion factors, circles, and pumping engine constants |
| Scale Length | 11” |
| Type of Rule | Other |
| Construction | Boxwood & brass |
| Area of Use | Other |
| Comment | A 2-foot, 2-fold rule used for engineering.
Joshua Routledge’s slide rule is the father of the engineering 2-foot, 2-fold slide rules, whereby sometime in the early 19th century, he took a Soho engineering slide rule and put these scales on one leg of a folding slide rule, added an incredible collection of constants applicable to engineering of all sorts, but particularly the design of steam engines, and so the first of the engineering slide rules in this format was born. Virtually every folding rule maker of any repute had a Routledge as part of their catalogue; examples such as this splendid example from the maker Hotltzapffel & Co of London (1797 – 1914) included other engineering items such as a protractor and spirit level. |
| Rarity | RR |
| Donor | Collection of an English gentleman. |
| Match Number | 63 |
| Thumbnail |  |
| RR | = Rare -- 1 of 25 collectors has one; it may take a year to find an example in the marketplace. |
| RRR | = Very rare -- only very few known to collectors; may take several years before one comes up for sale. |
| RRRR | = Extremely rare -- a museum piece; unlikely that an example will ever come up for sale. |