Although many sailors nowadays simply weld together the polyester cut ends of a mooring or fender line, nothing looks more professional than a crown or back splice to stop the ends of the lines from fraying. Once you have the hang of it, it only takes a few minutes to make the best of finishing touches to these lines.
It’s common nowadays to use sheaved ropes for mooring and fender lines but three strand polyester or nylon is much better. They can easily be eye spiced onto fenders and crown spliced at the bitter end to finish them off and if one part of the line is wearing it can be shorted or cut and respliced very simply.
Note: Try to use floating nylon mooring lines where possible, they are much more elastic than polyester and don’t drop to the seabed and snag up on rocks or coral.