| 摘要 |
<p>The ladder is used in scaffolding, with planks laid on rungs to serve as working platforms. Each rung comprises a metal tube, with a round piece (26, 28) at each end running across its longitudinal axis, fixed in it. A threaded lug (30, 32), running along the line of the rung, it attached to each round piece, to protrude from the rung. These pass through the stringers (10, 12), when built in and can be screwed outside to hold rungs in place. They may engage circular grooves (20, 22) in the stringers.</p> |
