Abstract: A device for producing a force when in a moving fluid, such as air or water, and a method for using said device. The device may be placed in a fluid moving in a first direction for producing a force in a second direction, which is substantially transverse with respect to the first direction. The device avoids the use of large sail areas needed where the force derived from wind is proportional to said area. The device according to the invention comprises an elongated body having in cross-section a rounded symmetrical profile, which defines an elongated and rounded leading portion whose thickness increases from the front to the rear and a rounded trailing portion whose thickness decreases from the front to the rear, the leading portion being longer than the trailing portion. The device according to the invention is also provided with at least one flap, which projects from the body and which is located on the trailing portion of the profile.