A roofer, roofing technician, or roofing contractor, is a tradesman who specializes in roof repair. Roofers repair, replace, and installs the roofs of commercial buildings, using various materials, such as asphalt shingles, gypsum, and tile. They also repair and install wood shakes, metal roof sheets, metal roof tiles, insulation, attic insulation, chimney mortar, gutter and attic cleaning, metal flashing, and roof repair. The roofing industry employs more than eighty percent of all construction workers.