A buffet meal is usually much less expensive than a served meal and involves the guests rising from their seats and visiting the buffet table where the offerings of the meal are displayed. They either serve themselves, or are served by employees of the catering service or venue. When the meal includes individually portioned items, such as chicken cordon bleu, it is wise to have servers at the buffet so as to avoid guests serving themselves two portions, resulting in a shortage of the main course. Buffet meals are usually billed by the number of guests invited as that is the number the meal is prepared for. Some vendors charge by the number of plates used.