What are the functions of the three buttons on a Mercedes-Benz key?

[DiEmilio]

Mercedes-Benz keys have three buttons: unlock, lock, and open trunk. Unlock button: Pressing the unlock button once only opens the driver's door; pressing it twice unlocks all four doors. Lock button: This button is also commonly used. Pressing it locks all four doors, and it has a hidden small feature—remote window closing. Sometimes after turning off the engine and parking, you may realize you forgot to close the windows or sunroof. In this case, simply hold down the lock button on the remote key to remotely close all four windows and the sunroof. Trunk opening button: There is a button on the car key to open the trunk. You can hold down the trunk unlock button (some cars require pressing it twice), and the trunk will automatically pop open. Some vehicles, when the key is within range, allow you to open the trunk by simply making a lifting motion with your foot under the rear bumper.