The curved profile of a surfboard from nose to tail is called its rocker.
Rocker describes how much the board bends upward along its length when viewed from the side. A board with more rocker has a more pronounced curve, while a flatter board has less rocker. Designers tune this shape to influence speed, turning, stability, and how easily the board fits into a steep wave.
Shortboards commonly have noticeable nose and tail rocker because the curve helps surfers make tight turns and avoid catching the nose in critical sections. Longboards are often flatter, which helps them paddle efficiently and maintain speed across weaker waves, although their exact rocker varies by design.
Rocker is different from the rails, which are the board’s side edges, and the outline, which is its shape viewed from above. It is also distinct from the stringer, the longitudinal strip that often runs through the board’s center for strength.