FRP molding is a method for forming composite materials that combine reinforcing materials such as glass fiber with thermosetting resins. It is characterized by its light weight, high strength, corrosion resistance, and high degree of design freedom. Hand lay-up is the most basic method, where glass fiber mats or cloths are placed in a mold, and resin is manually impregnated and de-aired layer by layer. It is suitable for small-volume production and large or complex shapes, and while it requires less capital investment, the quality depends on the skill of the worker. On the other hand, spray-up involves simultaneously spraying resin and short-cut glass fibers (chopped strands) onto a mold with a spray gun, followed by de-airing with rollers. It offers higher productivity than hand lay-up and is suitable for mass production of relatively large products, but it may be inferior in terms of strength and surface smoothness. It is widely used in ships, bathtubs, septic tanks, water tanks, and automotive parts, among others.