A motor mover is a 12V motorized device which is clamped to a caravan or trailer chassis and connects to rollers attached to the caravan wheels which then propel the caravan in any chosen direction, controlled by a handset. Basically like a radio controlled car. This will give you the ability to move any single or twin axle in positions you would not be able to do by the towing vehicle, or by hand, thinking of a heavy twin axle!
Different brands and models have different features, but one thing they all have in common, they are either manual or automatic engaged. This means that the manual engagement needs to happen by hand using an engagement tool (like a metal wrench), where the automatic engagement uses the remote and built in actuators doing this job for you.
You need a proper battery and the added weight is around the 30~35kg per axle.
I install both types and different brands/models, please contact me for options and pricing.