| 摘要 |
<p>The present invention relates to a double fixing apparatus for levelling. The present invention includes a lower ruler (10) with graduation (11) on the front side thereof, which is formed in the shape of a long cylinder having the open top and the closed bottom; an upper ruler (20) with graduation (21) on the front side thereof and all sides thereof in a closed stick-shape. The upper ruler (20) is inserted into the lower ruler (10) in a sliding manner for adjusting the length. The double fixing apparatus for levelling also includes a vertical balance maintaining means (30) combined to the upper part of the lower ruler (10) to have the lower ruler (10) and the upper ruler (20) automatically aligned vertically. According to the present invention, a staff can be always installed vertically with accuracy, thereby enhancing the accuracy of levelling.</p> |
