The self-checkout process is usually carried out by consumers themselves, without assistance from other persons. It may, however, be necessary for an attendant to intervene in certain cases, such as to verify the shopper’s age or deal with security tags. It is therefore usual, for customer support and monitoring purposes, to install one attendant station for a number of self-checkout systems. Ideally one attendant supervises from four to eight systems, whereby the attendant should have visual contact to the systems.