The support rule is positioned as follows: on those walls where we are laying the tiles to the
bottom, we place the rule at the base of the second row of tiles, so as to begin from this tile
upwards.
On the wall of the bath, we start tiling from the border upwards, and wait to lay the intermediate tiles
until the bath is in place, so as to make its installation easier.
We position the rule with the help of rule supports, placing one end at the measurement resulting
from removing one tile at the base of the border. The other end is dealt with in a similar way,
checking with the help of a level that the position of the rule is on the same horizontal plane.
