| 摘要 |
<p>The base has two free and curved tracks (5, 6) that are arranged on a full surface of the base, and an anti-rotation device is arranged on a part of the base. A set of metal pivots is positioned on the anti-rotation device. An upper face (4) of the anti-rotation device is arranged in a curved manner, where the upper face is provided with plaster sections. A set of left rails and right rails is arranged on the upper face, and a repositioning unit allowing repositioning of the set of left rails and right rails. The left and right rails are arranged in a parallel manner.</p> |
