I have seen this done a few times. It is a way to sneak a few plays in before the half.
An interesting tactic was used in the 2010 Pop Warner Midget semi-final game. The Pirates started their drive with 15 seconds remaining until the half. Pirate coach sent in his backups on offense and ran an off-tackle play. He them called time out with .6 seconds remaining so he could run one final play with that same group, another off-tackle run. So in the matter of 15 seconds Jeff was able to get his backups a few more plays in the first half, in a situation many coaches would have overlooked. http://www.youthfootballonline.com/
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