Lamellar, fibre-reinforced plastic strips can be used to reinforce a linearly expanded or flat construction part having a support function against any bending stress to which it is exposed. The strips are usually applied to the construction from the outside, or from the inside in the case of hollow structures, and fixed by an adhesive. The lamellar strips are pretensed with a tensioning device, treated with adhesive in a pretensed state, and then moved to the area to be treated together with the tension device. The tension device is provisionally fixed to the construction with displaceable fixing devices and pressed against said construction. Thereafter the lamellar strips are pressed against the construction by means of an air bag or air hose until the adhesive has hardened.