If we want to join several slats or lengthen one of them and that the junction stripes are not seen we have the solution double thread screws. The upper part consists of a metric thread and the lower one is of a wooden thread with a central hexagonal part that facilitates its tightening or loosening by means Natural stone or concrete are widely used in domestic and office equipment Communication equipment assembly of ships and other machinery industries Construction of concrete slabs carpentry works framework plumbing internal and exterior conditioning renewal solar facilities on roof double threaded ask Galvanized steel Galvanized steel is a type of steel that is covered with several layers of zinc, so it has a protection against oxidation because of the humidity conditions and inclement weather that cause corrosion to appear in metal appears this makes it It is a more durable and resistant material to screw the screw is necessary a preliminary hole of the 80 mm screw Torx Coat Partially threaded screw developed for a better assembly of durable components The screws are recognized for their reliability simplicity and solidity important] guarantee of return of 100 of money if you have any problem with our product Contact us for a change or refund or reimbursement Please contact us about any questions or question we will be delighted to offer all our help for us.