Smoke deflectors, sometimes called "blinkers" in the UK because of their strong resemblance to the blinkers used on horses, and "elephant ears" in US railway slang, are vertical plates attached to each side of the smokebox at the front of a steam locomotive. They are designed to lift smoke away from the locomotive at speed so that the driver has better visibility.
Smoke deflectors became increasingly common on later steam locomotives because the uplift of smoke exiting the chimney had been reduced as the result of efficiency gains obtained by improved smokebox design and reduced back pressure on the cylinders. Some locomotives avoided the need for smoke deflectors through unconventional styling which had the same smoke-lifting effect, such as the LNER A4 class and SR Merchant Navy Class (as originally built).
Various styles of smoke deflectors have been used by different railway operators. However, many are essentially a variation of one of two designs of Windleitbleche (wind deflecting plates) developed by the Deutsche Reichsbahn-Gesellschaft (the German State Railway Company between the World Wars): the earlier, larger Wagner-type deflector, and the later, smaller Witte-type deflector.