摘要 |
<p>Frames (3) and beams (4) comprise pairs of semi-structures (1) that are retained by fixed supports (7,8). When a covering (5) has been riveted to the first of each pair of semi-structures, the first semi-structure is inverted and placed onto a fixed entry unit (15). Another covering is riveted to the second semi-structure which is placed over the first semi-structure.</p> |