| 摘要 |
<p>The blackboard can be folded up and each leg (3) of the support is formed by two wooden parts (3a,3b). The extremities of these overlap and are held together by a bolt (5). The opposite faces of the extremities have longitudinal grooves (4) which fit together to hold the two parts firmly together, when the bolt is tightened. When the bolt is loosened, the bottom part of the leg (3b) can swivel towards the top (3'b), so that it fits against the top part of the leg (3a).</p> |
