The Stabox™ is a box in which starter bars, with a 6 to 12 mm diameter, are folded, to facilitate the application of reinforcement elements that pass through a concrete construction joint, without drilling through the formwork! The box is made of a profiled steel plate, with folded stirrups aligned at determined spacing. It is covered with a lid along its entire length, and the ends are closed with plugs. The Stabox™ is fixed to the formwork panel of the first stage of concreting by ordinary nails (for timber panels) or by magnets (for metal formwork). The first stage of concreting anchors the bars that come out of the back of the box. After removal of the formwork, the lid is removed and the bars can be unfolded to form a link with the second stage of concreting.