| 摘要 |
The case (1) has an upper cylindrical section (2) with a concentric lower section (3) of reduced diameter. The transition between sections takes the form of an annular step (4) with a chamfered nose (5). Hollow columns (10), formed on the lower section's inner face, allow the case to be nailed to the form work supporting the ceiling at the construction stage, and the step is interrupted by e.g. 4 pairs of diametrically opposed notches (6), equally spaced around the case. Selecting one such pair, the installer sets on the horizontal bed of each notch one end of a cross-bar (11) carrying in a central position the load-bearing hook (12). The sides of each notch converge slightly towards the top, and finish there in slightly projecting lips, chamfered on their upper surface. The distance between the lips is slightly less than the overall width of the cross-bar end, measured across lips (13) molded on the lower edge of each side. The elasticity of the material allows the cross-bar to be pressed home against minimal resistance, but the lips prevent its being accidentally dislodged, though deliberate repositioning remains possible.
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