| 摘要 |
<p>The system locks a blackboard instantly at the desired height on fixed or movable posts. The locking device is a simple flexible bar (8). The ends of this flexible bar slot into two holes (6, 7) in slides placed on either side of the board. The bar presses the slides (3, 4) against the vertical supports (1, 2) on which the slides (3, 4) are mounted. Pressure on the middle part of the bar reduces its length and enables the slides to move along their supports.</p> |
