I'm planning on tiling a kitchen splashback (first time tiling project). Unfortunately due to curvature of the wall, there is a gap between the worktop and the wall. This varies in thickness between about 2mm and 9mm.
I feel that there is a good chance that the tiles will slip down into the gap behind the worktop. My question is therefore: How should I stop the tiles falling down into the gap, and instead keep a level first row?
So far I have considered:
Plugging the gap with a strip of wood. Seems ideal, but unfortunately I don't have a suitable piece of wood nor the tools to craft one, and it is difficult to get hold of this sort of thing at the moment!
Filling the gap with caulk/grout/filler. This would be easy enough, but could I get a level enough surface to start the tiling from?
Tiling off a metal rule. I can't re-find it now, but I read somewhere that you can lay the first set of tiles on top of a metal ruler – presumably laid flat on the worktop? Could this help to form a temporary 'bridge' over the gap?