I am planning to tile over an existing concrete slab in my backyard.
The slab is level from one side to another, but there is a gentle fall
from end to end. Although the slab is fine overall, there are a few
ups and downs and I want to make sure that the tiles don't have highs
and lows as I tile down the slope. I presume a string line would do
the trick, but perhaps someone has better ideas for the amateur.
Thanks Philip Lock