Your vehicle's internal combustion engine is made up of a wide range of parts, including the cylinder head. This head sits on top of the cylinders in the cylinder block and is fastened down with cylinder bolts. These bolts are an important part in the engine because they have to withstand an enormous amount of pressure coming from the cylinders in order to keep the head fastened. That's why it's important to make sure you use the right cylinder head bolts in your vehicle's engine, especially when you're installing a new gasket. The cylinder head bolts on some cars are what's known as 'stretch bolts' and are designed to only be used once - because they stretch!