Thread-forming screw, should it be pre-drilled first? Currently installing a roof ladder and in the bags with bolts, nuts, washers, etc. there seems to be what I thought were self-drilling screws. Should it be pre-drilled the thread-forming screw with sealing washer before fastening into the metal peaks?
Regards
Regards
Both types exist. The difference is visible at the end or front of the screw. The self-drilling one has a special tip that allows it to drill into the substrate. It sometimes looks like a small pointed spoon at the front.
