These 2-in. by 12-in. side boards were retrofitted to the K-series tenders in the 1930s, when the railroad needed to increase coal capacity. Trains were longer and heavier, revenues were down, and locomotives were required to work more mileage between coalings. Instead of building additional coaling facilities or engine terminals on the narrow gauge line, management added the side boards, which were cheaper. They have never been removed and still serve a useful purpose--increasing capacity by more than ¾-ton. Not all locomotives have (or need) side boards but the D&SNG and C&TS Mikes are so equipped.