Due to the shape of the face, the tiles are divided into two types:
a) for flat tiles with a completely flat grain surface,
b) on chamfered tiles, i.e.. having diagonally trimmed edges.

Among flat tiles, depending on the purpose, there are middle and corner tiles. Besides, the middle coronary, or footer, corner ring or foot plates, box bases, the so-called. chocolate and rosettes, that is, traffic jams.

Chamfered tiles: a) middle, b) corner.

Among the chamfered tiles we have middle and corner tiles.
Depending on the defects in the tiles, we divide them, in accordance with the above-mentioned standard, and 3 species. Grade I tiles should have parallel edges forming a right angle between them. The visible surface should be even, and the enamel is smooth and uniform in color. The concavities or convexities in the visible surface should not be greater than 1 mm for tiles with white glaze and 1,5 mm - for tiles with colored glaze.

The tiles should not have cracks or defects in the shell, what we can tell from the clear sound when tapping the tiles with a hammer. Covering glaze should not have hairline scratches, i.e. the so-called. ceku.
The "on the cek" enamel examination is carried out in this way, that the tiles are placed in a vessel with water on 24 hours, and after removing the tile, the glaze is covered with black paint or ink to show hairline scratches.
Apart from the "on" test, the tiles should be inspected and their external condition checked; correctness of shapes, the parallelism of the edges and the smoothness of the surface.
Detailed laboratory tests are performed in the event of suspicion that the delivered batch of tiles is of poor quality. The tests are then carried out in accordance with PN-58 / B-12041.
The requirements for II and III grade tiles are also specified in the aforementioned standard.
The tiles are usually ordered and delivered to the construction site in stove sets, where a certain number of tiles, the so-called. furnace (placed on the side of the wall) it may be II or III species. However, it is better to purchase the tiles individually, specifying the number of middle and corner tiles according to the calculation.