| 摘要 |
A bridge (1) is provided which has laterally projecting pins (8,10) which are pivotably located in holes (12) positioned at various levels in a series in feet (9,11). This enables the bridge to be pivoted between an inclined position with its one end (2) located against the ground and an approx. horizontal position with its other end (3) ar pref. a lower level than the first. At its second end, the bridge has a stop (4) preventing the wheel rolling off it. The pins nearest the first end are so far from the stop that the wheel centre can pass inwards against the stop. |
