The work of valve is difficult and it needs the specialized equipment and tools used, hence a professional should service the valves, valve seats and valve guides, which is also known as a valve job. A home mechanic may take the head(s) off-site and strip them down, perform some initial clearing and inspection, and then reassemble them and ship them to a dealer service department or an automotive machine shop where the actual work would be done. The inspection will make it possible to examine the state of the head(s), as well as valve train, components, being aware of the work and new parts required when dealing with an automotive machine shop. The dealer service department or automotive machine shop will do the process of removing the valves and springs, reconditioning or replacing the valves and valve seats, reconditioning the valve guides, checking and replacing the valve springs, spring retainers, and keepers as necessary, replacing the valve seals with new ones, and reassembling the valve parts and ensuring that the correct spring height is installed. Also resurfacing of the cylinder head gasket surface will be done in the event it is warped. After the work of a valve is done by a professional, the head(s) will be in the condition of a new one. When they come back they should be again cleaned and before putting them back on the engine, it is important to clear them off any metal particle and abrasive grit that might be left behind during the valve service or head resurfacing procedure and also use compressed air to blow out every oil hole and passage.