Can you conduct a file from the left/right from a mark time?

FM 3-21.5
6-9
b. Forming a file from a column of twos is executed only from the Halt. The
command is File from the Left (Right), MARCH. On the preparatory command, the lead
team leader commands FORWARD. The trailing team leader commands STAND
FAST. On the command of execution MARCH, the lead team marches forward. The
trailing team leader commands Column Half Left (Right) when the second man from the
rear of the lead team is abreast. He gives the command MARCH when the last man of
the lead team is abreast of him and his right foot strikes the marching surface. He then
inclines right or left to follow the lead team at the correct distance.

The position of attention is the KEY position for ALL stationary, facing, and marching movements. Just remember this sentence when in doubt.