Rubi battens (although I don't like them) and I use old levels as the straight ledge. I sometimes put blobs of silicone to stick them to the wall. I also use slithers of tile to stop them sagging in the middle.
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Never use battons......if the tiles are not heavy then draw a line half way up the wall and tile down using a non slip adhesive.......With heavy tiles cut the first row in and tile up....I find it much quicker doing it this way
Non slip adhesive moves a slight touch does it not?
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