In an automobile, gaskets are thin sheets of flexible materials that are used to separate two metal components. They allow metal parts to be mated together without losing fluids that are transferred between the two. Normally when two pieces of metal are mated, there are minute machining differences in the surfaces that would allow high pressure fluids or gasses to escape and relieve pressure. In an internal combustion engine, fluid flow between parts is vital for engine operation. Gaskets help the engine transfer these fluids with less loss. Gaskets are commonly made from brass, steel, and rubber compounds. In addition to proving more conducive passages for fluids to flow, they also serve as insulation to isolate some parts from shock or vibrations that could cause leaks, and create tighter fitting parts that are more likely to stay in place.