| 摘要 |
<p>The mechanism is used to adjust the height of a mast, even at sea, by means of a crank welded to the end of a retraction screw. The screw slides the movable plate accommodating the mast foot to and fro. There is a recess in the fixed plate, so it is unnecessary to fit a block in the bottom of the boat to hold the mast firmly in position.</p> |
