I've just replaced the floor in my bathroom and as I prepare to put the vanity back (we removed it to lay floor under it in the spirit of completeness) I've discovered why combs and things fall down the side of the vanity so often (what a trove we found when we took it out.) The wall is not square:
The wall takes a turn just before the corner and seems like it's thicker. This means the vanity does not sit squarely in the corner. We were thinking of putting tiles on the wall just above the vanity to cover this gap (and we still might) but we may have other options.
First, I can put a shim at the top left corner in this picture, so that the vanity is evenly out from the unsquare wall, and sits squarely in the room, which should stop the gap at the side, which is where everything fell. The back of the vanity comes up in an L shape to form a very short backsplash (maybe 2 inches) so stuff doesn't fall in that direction. But the gap between the wall and the backsplash will be noticeable (even more than it is today), so we would still want to do the tiles. But the non squareness of the wall may be emphasized by trying to attach a tile border to it.
I can't plane the back of the cabinet, because this backsplash is some sort of ceramic. I'm considering getting a thickish piece of wood and planing some off the back of it to match where the wall swells so that the front of the wood forms a square surface, attaching it to studs just above the backsplash, painting the wood the same colour as the wall (white) and then attaching the tile to the wood, presumably resulting in a border of tiles that is nice and even. Is this sensible? Overkill?
Could I instead chisel a bit of a channel into the wall and set the last tile into that so it is still even? Which is more work, chiseling the wall or planing and then attaching the wood?