In the United States Military, Preventive Maintenance Checks and Services, or PMCS, (also known in the US Air Force as Preventative Maintenance Inspections or PMI), are the checks, service and maintenance performed before, during, and after any type of movement or before the use of all types of military equipment. Most pieces of military equipment have a PMCS chart used to go over every detail needed or noted to ensure the proper function of every mechanical item or non-mechanical surface. A PMCS check is required before, during and after a piece of equipment or vehicle is used. Checks are also done at weekly, monthly, semi-annual, annual, and bi-annual intervals, depending on the specific part.