service door
service entrance
servant's entrance

I let myself in through a service door on the terrace.

"Funny he did not just go to the service door and ask for me, wasn't it?"

A service door to the roof would give the creep a way out.

Please exit quickly, enter the service door at once, and close it behind you.

While he did so, I'd get out through the service door by the food service core.

However, if you wish to leave without seeing me, use the service door.

I went back along the hall and tried the service door.

We left the ground floor through a service door.

He walked across to the service door and opened it.

Garbage has started to smell beyond the service door of your apartment.