| 摘要 |
This invention relates generally to screw-type fasteners of the type adapted for use with panels comprising insulation material bounded by sheet material on one side and a thicker purlin material on the other side. The fastener includes three sections of thread convolutions. The first section is located directly beneath the head of the fastener and extends for a short axial distance. The second section is located near the drilling point of the fastener and is adapted to fasten to the thick sheet of purlin material comprising part of the panel. The intermediate or third section is utilized to prevent the fastener from falling freely through the insulating material and thus prevents possible breaking of the drilling tip or cocking of the fastener out of the perpendicular plane.
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