[dubc80]

When people don't open the car wash door to signal that they are done.

Sometimes the doors are all dirty, fogged up, or even made of solid materials, so it can be challenging to see inside.

So, you basically have to open the door every few minutes to check and inevitably get a dirty look if the person is still washing.

There's really no other way though. Otherwise you run the risk of just sitting there and the guy has already left out the other side.