The user of the product has considerable influence on purchasing. The user is the employee using the product, not the patient on whom it is used. However, the considerable endeavour to involve users aims to take account of their knowledge of products and manufacturers. A head of a medical physics department said that the main reason for carrying out 'in house' service and maintenance is to avoid manufacturers' costs, but felt that works staff extend their servicing role beyond electrical plug changing and other minor repairs. The use of manufactured products is an important part of modern medicine, but the relationship between the product and the patient is by no means simple. Considerable efforts are made by supplies officers to involve medical and nursing staff in choosing products that can become standard in their area or region and numerous committees exist for this purpose.