It should not be done differently for a period exceeding 7 mm and a length of 20 cm should not have done differently than 2 mm surface conditions must be suitable, there are no abnormalities.
There should not be a difference of up to 7 mm and 20 cm for the length should not exceed 2 mm, a different flat surfaces must be smooth and without irregularities.
There should not be different than the flatness 7 mm and for the length 20 cm. There should not be different than the flatness 2 mm. The surface must be smooth without normal.