The more I look at the command of REST in context with the other manners of standing in formation, the more I believe it means the men have to remain in ranks, but without maintaining either foot or both feet on the supposed line as seen in the other forms of rest.
For example, when at Attention, both heels are on the line. When at one of the rest positions while carrying the weapon (parade rest, in place rest, or support rest), one heel remains on the line. By implication, plain old REST means no heels on the line. If a captain intends for the men to leave formation entirely, the command is Break Ranks, March.
- Silas Tackitt
"I consider him a humbug, a man of small capacity, very obstinate, not at all chivalrous, exceedingly conceited, and totally selfish." - - Lafayette McLaws about James Longstreet.