In aerodynamics, a stabilizer is a vertical or horizontal fin that prevents erratic rolling (see roll) or pitching (pitch), respectively. Stabilizers are usually placed together in the form of a tailplane. Like the wings, the horizontal fins have an airfoil shape and can provide lift at take-off. In flight, however, they act only as stabilizers and in some designs the air thrust on them acts downward. In marine engineering, fins or tanks are used to keep a submarine or ship steady in rough seas.