Abstract: A structural element, such as a section of a duckboard (e.g. a landing mat) to be removably fastened to a similar section, has one or more edges provided with male coupling formations adapted to be converted into complementary female formations by breaking off a projecting part thereof. The projecting part is generally T-shaped, with its frangible stem rising from the bottom of a preferably dovetail-shaped recess. Such an element can therefore be readily joined to another element having a mortise complementary to the head of the T or a tenon complementary to the recess.