Important safety notes

WARNING When leaving the vehicle, always remove the 
When leaving the vehicle, always remove the SmartKey from the ignition lock. Always take the SmartKey with you and lock the vehicle.
Do not leave children unsupervised in the vehicle, even if they are secured in a child restraint system, and do not give them access to an unlocked vehicle. A child's unsupervised access to a vehicle could result in an accident and/or serious personal injury. They could:
injure themselves on vehicle parts
be seriously or fatally injured by extreme heat or cold
injure themselves or have an accident with vehicle equipment that may still be in operation even after the SmartKey has been removed from the ignition, such as the seat adjustment, steering wheel adjustment or memory function.
If children open a door, they could cause severe or even fatal injury to other persons; if they get out of the vehicle, they could injure themselves when doing so or be seriously or even fatally injured by any passing traffic.
Do not expose the child restraint system to direct sunlight. The child restraint system's metal parts, for example, could become very hot, and a child could be burned on these parts.

WARNING If a key ring is too heavy or too large, the 
If a key ring is too heavy or too large, the weight acting on the key could cause it to turn in the ignition lock or catch on the steering wheel. This could cause the engine to be switched off suddenly. You could lose control of the vehicle and cause an accident. Do not attach any heavy or large key rings to the key that is inserted in the ignition.

    See also:

    Cargo & Towing
    When properly equipped with the optional trailer hitch, the GLK350 is rated to tow up to 3,500 pounds. ...

    Position of the steering wheel when the EASY-ENTRY/EXIT feature is active
    The steering wheel swings upwards when you: remove the SmartKey from the ignition lock open the driver's door and KEYLESS-GO is in position 1 open the driver's door and the SmartKey is ...

    Opening/closing the garage door
    Once programmed, the integrated garage door opener will assume the function of the garage door system's remote control. Please also read the operating instructions for the garage door system. ...