English: Rural Free Delivery (RFD) carrier Harold Crabtree of Central Square, New York, used this 1921 Ford Model-T. The front wheels were interchangeable with skis and the rear tires accommodated tank-like treads, allowing the vehicle to move more easily over snow and ice. The attachment, named Snowbird, was manufactured by F.S. Manufacturing Company of New Holstein, Wisconsin. The company advertised it as the “mailman’s special.” Manufacturers advertised the snowmobile attachment as easy to install. Northern carriers who had purchased automobiles for their routes learned quickly that their new cars were often no match for deep snow. For many, the only option was to use their horses and old wagons during bad winters. The Snowmobile Company of West Ossipee, New Hampshire, was talking to those carriers when it asked them to consider if they could “afford to own and feed horses 12 months in the year simply for use during the winter season?” Just as they had done with their wagons in years past (switching the body of their RFD wagon from wagon wheels to runners for the winter months), carriers began using snowmobile attachments on their automobiles.