Fired clay hollow bricks [CLBRH]

Fired perforated clay bricks with one or more holes (cavities) through the thickness of the brick with the area of cavities in excess of 25% of the volume. The holes can be seen from above after the brick has been laid.

Fired clay hollow bricks, Iran (A. Charleson)

Fired clay hollow bricks with vertical perforations, Peru (S. Brzev)