depends what you want it to do!
I had one lying about so I made a quick connect for my jump leads. mounted it to the battery box.
I also have a set of smaller 50amp ones lying around which I was going to use for my fridge, but no longer need it.
Can be used to connect power to trailers, solar panels, battery chargers, allsorts really - anything that needs a remote connection requiring med to high ampage draw.
G