Diamonds are a tile cutter's best friend - now that's a fix for that stupid saying!
I urge you to take a quick look at your bathroom. Or your kitchen. Some of us would like to live in a world where the width and height of the area being tiled would accept an exact, total, complete, 'point-zero' number of tiles.
Sadly, that is rarely true (but a great idea for an architecture firm, eh? - specializing on designing rooms based on the tile dimensions!).
So, to cover that last bit of wall, you'll need to cut a tile or two with this little device here.
UK plug.
Please give this a good clean, and empty it out before use and before returning it. No one wants a grubby tile cutter, or a stern look from a librarian.