Jinshanling Service Area. What exactly do the "service area" refer to?

The service area is actually a resting zone by the highway and the coach will stop there. Once alighted, you will be transferred to the Wall by a free shuttle bus.
The service area is a few miles away from the scenic area. You can buy tickets when you get to the Wall.
After hiking, you may get back to the main gate of the scenic area to find the shuttle bus at the square. Take it to the service area to take the return trip bus.

Krisjanis,

The service area is a gas station, convenience store, and restroom and is right off of the highway a few miles from the ticket counter/wall entrance. There may or may not be a free shuttle at the time you arrive. If there is not, then there will likely be taxi drivers around who will approach you and offer to take you to the wall entrance. I took one of these taxis and was pleased. It was a little pricey but it was either walk a few miles and run out of time or pay a little. As far as return, the taxi helped in this regard. The taxi driver met us at the wall entrance at 3PM and took us back up to the "service area" where a bus returning to BJ picked us up at about 3:40. You should be prepared to pay a taxi driver a couple hundred yuan to get you to BJ if you don't get on the return bus (sometimes seating is limited). I know that some folks did not make it on the return bus when I went and do not know whether there was another coach after the one I took.