what does this fuse do?

I have a fuse that runs loosely across the in car fuse board. Its in its own independent fuse box, yellow and has black electric tape wrapped around the wires.
Is this supposed to be there if so what for.
Or is it aftermarket.
Thanks

Photos might help.
Yellow wires are usually to do with the air bag

Aftermarket from your description , has it had a tow bar fitted?

I take it as a yellow box it could either be for spot lamps or like said tow bar what extra's do you have on it, remove the fuse and see what does not turn on.

Sorry I meant it was a yellow fuse, I couldn't remember the rating.
Spot lights I fitted myself so I know its not that,
It did however come with a tow bar, I presumed it was factory. But after what you have said, if its aftermarket that can be the only other thing I haven't fitted myself. The fuse holder etc certainly looks aftermarket. So I'm going to say its for the tow bar. Thanks for your help guys!