Workers often carry materials with
them...especially when the workers drive trucks or other vehicles. Occasionally,
it might be important to know when a part is on a truck-if you need a
particular part in a hurry, it's nice for MainBoss to be able to tell you, "Joe
has one of those in his truck."
The obvious solution is to treat trucks as storerooms. In MainBoss, you might create a special Location record called "In Transit". Under this location, you can create Storeroom records for each truck. When you put materials onto a truck, you record this as a transfer to a storeroom; when these materials are used on a job, you record it as a usage from the truck "storeroom."
In this way, not only do you know what's in your storerooms, you also know what's in your trucks. That way, MainBoss has a complete picture of where your materials are.