Rubble masonry is rough, uneven building stone Small Peices of rocks (Karinkallu) set in mortar but not laid in regular courses It may appear as the outer surface of a wall or may fill the core of a wall which is faced with unit masonry such as brick or ashler. Analogously, some medieval cathedral walls are outer shells of ashlar with an inner backfill of mortarless rubble and dirt. The "modern" brickwork is made with a concrete casting without any elements and with an internal steel reinforcement. This allows for greater elasticity, excellent static and seismic resistance and preserves the unity between shape and structure typical of buildings with external load-bearing walls. All the structural tasks can be assigned to the sack walls thus created, freeing the internal spaces from excessive constraints.