My savings grace has always been the manufacturer manuals of all of the installed items. I make sure I have one of these manufacturer manuals for all my installed individual units. You can go on-line and find any and all of these PDFs by just posting the model number...
This undoubtedly saves the companies alot of money not having to identify all the different models of their fleets...
Definitely JAYCO is one of the great companies that will forward you the trailer build drawings etc in PDF email format just for the asking. All you need is your trailer VIN number...
Roy Ken