Material constraints

I am trying to get MRP to function properly in Vantage 8.03.405. I have read thru the help sections a few times and i want to make sure I understand properly. If you do not flag a part as constrained the job scheduler will assume there is no leadtime for materials and not delay the start or end of the job?

What do other people do for constraints and trying to schedule workload?

Thanks,

Adam Riffer
IQuum, Inc.