Waiting for the part to be delivered is NOT a task unless the delivery
process itself requires work by a resource that must be scheduled. If I
order a part and am waiting for it to come, the tasks involved are the order
process itself, taking however long it takes me to place the order, and the
task that uses the part once it gets here. If it will take two weeks to
deliver, then there is a 2week lag time in the link between the "ordering"
and the "using" tasks. On the other hand, if one of my resources has to
take a truck to the vendor, pick up the part, and drive back to deliver it,
that lag time becomes instead an actual task with a two week duration and
requiring the driver as a resource assigned probably 100%.