213.  As the communications containing the parole and countersign must at times be distributed by many orderlies, the parole intrusted to many officers, and the countersign and parole to many officers and sentinels, and as both the countersign and parole must, for large commands, be prepared several days in advance, there is always danger of their being lost or becoming known to persons who would make improper use of them; moreover, a sentinel is too apt to take it for granted that any person who gives the right countersign is what he represents himself to be; hence for outpost duty there is greater security in omitting the use of the countersign and parole, or in using them with great caution.  The chief reliance should be upon personal recognition or identification of all persons claiming authority to pass.

Persons whose sole means of identification is the countersign, or concerning whose authority to pass there is a reasonable doubt, should not be allowed to pass without the authority of the corporal of the guard after proper investigation; the corporal will take to his next superior any person about whom he is not competent to decide.

214.  The COUNTERSIGN is usually the name of a battle; the PAROLE, that of a general or other distinguished person.

215.  When they can not be communicated daily, a series of words for some days in advance may be sent to posts or detachments that are to use the same parole or countersign as the main body.

216.  If the countersign be lost, or if a member of the guard deserts with it, the commander on the spot will substitute another for it and report the case at once to headquarters.

217.  In addition to the countersign, use may be made of pre-concerted signals, such as striking the rifle with the hand or striking the hands together a certain number of times as agreed upon.  Such signals may be used only by guards that occupy exposed points.

They are used before the countersign is given and must not be communicated to anyone not entitled to know the countersign.  Their use is intended to prevent the surprise of a sentinel.

In the daytime signals such as raising a cap or a handkerchief in a prearranged manner may be used by sentinels to communicate with the guard or with each other.

SECTION 12.  GUARD PATROLS.

218.  A guard patrol consists of one or more men detailed for the performance of some special service connected with guard duty.

219.  If the patrol be required to go beyond the chain of sentinels, the officer or noncommissioned officer in charge will be furnished with the countersign and the outposts and sentinels warned.

220.  If challenged by a sentinel, the patrol is halted by its commander, and the noncommissioned officer accompanying it advances alone and gives the countersign.

SECTION 13.  WATCHMEN.