Automatic/manual door lock with servo I'm building an automatic door lock, which is moved by a servo ( this one ). However, I want to still make it possible to open the lock manually, but it's not possible if the servo is attached to the lock mechanism.

Do you have ideas on how to go around this problem?

Here's a diagram of the lock mechanism
So it's actually the worm gear that is causing your problem, since that can't be reverse driven by the cogs.

The simplest option, I think, would be to have the middle cog normally separated from the worm gear and only re-engage it when you need to drive the mechanism with the servo.  You could maybe use a second servo to move it into the right place, or maybe a solenoid, or something along those lines. Have it slide along a short track or slot with a spring to ensure it disengages when the solenoid is released.