_ The element on which a movement is regulated.

_Battle sight:_ The position of the rear sight when the leaf is laid
down.

_Center:_ The middle point or element of a command.

_Column:_ A formation in which the elements are placed one behind
another.

_Deploy:_ To extend the front. In general to change from column to
line, or from close order to extended order.

_Depth:_ The space from head to rear of any formation, including the
leading and rear elements. The depth of a man is assumed to be 12
inches.

_Distance:_ Space between elements in the direction of depth. Distance
is measured from the back of the man in front to the breast of the man
in rear. The distance between ranks is 40 inches in both line and
column.

_Element:_ A file, squad, platoon, company, or larger body, forming
part of a still larger body.

_File:_ Two men, the front-rank man and the corresponding man of the
rear rank. The front-rank man is the _file leader_. A file which has
no rear-rank man is a _blank file_. The term _file_ applies also to a
single man in a single-rank formation.

_File closers:_ Such officers and noncommissioned officers of a
company as are posted in rear of the line. For convenience, all men
posted in the line of file closers.

_Flank:_ The right or left of a command in line or in column; also the
element on the right or left of the line.

_Formation:_ Arrangement of the elements of a command. The placing of
all fractions in their order in line, in column, or for battle.

_Front:_ The space, in width, occupied by an element, either in line
or in column. The front of a man is assumed to be 22 inches. Front
also denotes the direction of the enemy.

_Guide:_ An officer, noncommissioned officer, or private upon whom the
command or elements thereof regulates its march.

_Head:_ The leading element of a column.

_Interval:_ Space between elements of the same line. The interval
between men in ranks is 4 inches and is measured from elbow to elbow.
Between companies, squads, etc., it is measured from the left elbow of
the left man or guide of the group on the right, to the right elbow of
the right man or guide of the group on the left.

_Left:_ The left extremity or element of a body of troops.

_Line:_ A formation in which the different elements are abreast of
each other.

_Order, close:_ The formation in which the units, in double rank, are
arranged in line or in column with normal intervals and distances.