When you arrive unexpectedly at someone's house you go in through the front door, often after making sure you've got a couple of mates waiting round the back. For a business, especially the kind that involves big trucks and heavy metal, it's always better to go in through the back. The customer-facing part of any modern business is purposely designed to be as politely unhelpful as possible. If you go in from the rear, the customer-facing staff are all facing the wrong way and everybody starts their conversation on the back foot.