A fairlead, also known as a "bulwark cable hole," is a closed-hole type fairlead installed on the bulwark to restrict the exit position of cables. It is a circular or oval-shaped ring casting. Fairleads are typically made of cast iron or cast steel, mounted on the bulwark to guide cables through the hull and prevent damage to the hull.

The production method of pouring molten metal into a mold cavity that matches the shape and size of the part, allowing it to cool and solidify to obtain a blank or part, is commonly referred to as metal liquid forming or casting. Liquid metal forming processes, unlike lost foam casting, have the following characteristics: 1. Capable of producing parts with arbitrarily complex shapes, especially those with intricate internal cavities. 2. High adaptability, with no restrictions on the types of alloys, and almost no limitations on the size of castings. 3. Wide range of material sources, recyclability of scrap products, and low equipment investment. 4. High scrap rate, relatively low surface quality, and poor working conditions.

When designing the gating system for lost foam steel castings, it should facilitate exhaust: White mold undergoes pyrolysis under the influence of high-temperature alloy solutions, rapidly decomposing at 1350~1550°C, with released H2 reaching up to 48%; polystyrene releases gases such as CnH2n, H2, and CH4 during pyrolysis, with volumes of 165~175 cm3/g at 800°C, 500~518 cm3/g at 1000°C, and 738~6 cm3/g at 1200°C.