Since most military posts or bases are guarded on a twenty-four hour basis, the first official contact will be with the guard on the main gate. He may be a soldier or airman selected by roster and under the temporary control of the Officer of the Day, a Military Policeman wearing an MP brassard and under the command of the Provost Marshal, or a civilian guard either under the Provost or some other special staff agency of the Post or Base Commander. On the ordinary post or base, officers of other services will be admitted if wearing uniform, even when accompanied by civilian dependents. If the stay is of short duration, a "visitors" tag on the car may be sufficient; in other cases it may be necessary to secure a temporary pass from the Provost. Except for civilian guards, who do not salute, and who will be readily identified in their police uniforms, the guard, if armed with a pistol or carbine will give a hand salute. During the hours for challenging (usually extending from a short time before darkness until after reveille the next morning) sentries on an Army post may require any officer to halt, give his rank and name, and advance for recognition. The challenging sentry stands at "raise pistol" or "port arms" until the challenged party has been recognized, after which he simply returns his weapon to the normal carrying position; if armed with a rifle, he executes "present arms" and holds it until the salute is returned. On any post or base, the adjutant usually acts for the commanding officer in greeting the visitor and directing him to the various facilities of the base, although if the visit is to be of short duration--say, just for the purpose of seeing a friend--it would be impertinent to bother him. But if the visiting officer is reporting for temporary duty, or if he will be living in the immediate vicinity for some time on special detail and desires the use of post facilities, he is required to report to the adjutant. Most posts and bases have not only a bachelor officers quarters, more popularly known by the abbreviation BOQ, where the visitor may obtain lodging, but also a Hostess House where the officer may stay with his dependents. These accommodations are usually under the supervision of the Billeting Officer, who makes the assignments and charges a nominal fee for the services provided. Other facilities that the visitor may use include the Officer's Club and dining room, the Post Exchange (corresponding to Navy Exchanges), and the post theater. Under certain conditions the visitor may secure permission from the adjutant or executive to make purchases at the Commissary, which deals in foodstuffs and other perishables.