The Certes was a manual roller mower made specifically for use on putting and bowling greens where a high quality machine was required to produce the finest possible cut.
Made by Ransomes, Sims & Jefferies of Ipswich, the Certes was introduced in the late 1920s and continued in production until the 1970s. The design remained largely unchanged throughout the production period, although a number of minor improvements were made with the introduction of each new mark. Models with 12in and 14" cutting widths. Ransomes also produced a mower known as the Overgreen that incorporated a number of Certes chassis in a 3, 5, 7 or 9 unit gang configuration.
The Certes was designed to be used by professional green keepers who needed a precise mower to prepare sports playing surfaces. Compared with domestic mowers of similar appearance the Certes featured higher quality materials machined more exactly. It had a more robust frame, a heavier roller and a cutting cylinder (reel) with more blades. The result was an extremely resilient mower that could be set to exact tolerances to give a very close finish on lawns.
Generally, the quality of cut from a mower depends on the number of cuts made per inch of forward travel across the lawn. Many people assume that the more blades on the reel the better, but in reality the number of cuts per inch also depends on the number of time the cylinder turns in any given distance. In other words, a lower number of blades turning more quickly will give as many cuts per inch as more blades turning slowly. However, this requires higher gearing which makes it more difficult to push the mower and achieve a consistent cut. The Certes therefore has a higher number of blades on its cylinder than similar domestic mowers.
The Certes is prized among collectors for its quality of cut. Many are still in use.