Pipe Winding Building Flanges and Fittings Fabrication of Piping Spools Cutting and drilling operations Repair and replacement of existing piping systems Release air bubbles and smooth seams, using rollers Select and cut fiberglass mats and cloth as required by items being made Pat or press layers of saturated mat or cloth into place on molds, using brushes or hands, and smooth out wrinkles and air bubbles with hands or rollers Mix catalysts into resins, and saturate cloth and mats with mixtures, using brushes Check completed products for conformance to specifications and for defects by measuring with rulers or micrometers, by checking them visually, or by tapping them to detect bubbles or dead spots. Trim excess materials from molds, using hand shears or trimming knives Repair or modify damaged or defective glass-fiber parts, checking thicknesses, densities, and contours to ensure a close fit after repair Cure materials by letting them set at room temperature, placing them under heat lamps, or baking them in ovens.