Metal roof provides increased wind resistance when compared to other roofing materials. This is because metal roofing systems use interlocking panels. The disadvantages of metal roofs include the noise created from rain hitting the roof, and, in snowy areas, the tendency of snow to easily fall off the roof and onto pedestrians or property. Originally, metal roofs were made of corrugated galvanized steel: a wrought iron–steel sheet was coated with zinc and then roll-formed into corrugated sheets. Another approach is to blend zinc, aluminum, and silicon-coated steel. These products are sold under various trade names like "Zincalume" or "Galvalume". The surface may
Coated abrasive sanders, die grinders and belt sanders The first recorded use of a coated abrasive is from the 13th Century, when the Chinese bonded crushed sea shells to parchment using natural gum. A quick change system is commonly used with disc type coated abrasives. A plastic or metal hub is bonded to one of the faces, which is threaded. This then mates directly to the sander/grinder or to a mandrel that can be mounted in a sander, grinder, or drill. The advantage is that the disc can be quickly replaced when needed. Quick change discs range in sizes from to no