| 摘要 |
In a washer, a central opening is provided for receiving a screw. This large surface-area washer comprises a flat edge area extending so as to be closed with a convexly curved portion adjoining the latter. The central opening is defined by a wall which is conically shaped or comprises one or more steps. The washer serves to fasten parts to an underlying structure, particularly to fasten single-layer or multiple-layer roofing with insulating material on a fixed underlying structure.
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