Tonneau is the flat cover for the bed. A cap is the n-shaped cover that encloses it, giving it a roof. Typically matching the cab body work, so overall looks mo

Tonneau is the flat cover for the bed. A cap is the n-shaped cover that encloses it, giving it a roof. Typically matching the cab body work, so overall looks more like an SUV. Eg: http://trinity-motorsports.com/wp-content/uploads/2016/07/2016-Ford-F-150-bed-cap-3.jpg http://trinity-motorsports.com/wp-content/uploads/2016/07/20...