Pictish art appears on stones, metalwork and small objects of stone and bone. He enjoyed building granite sculptures and structures with local stone and cement. They used tools made of stone and wood. Retaining walls resist movement of earth, stone, or water. It is made from clay with a small percentage of crushed stone. It is a small square pillar stone. This utilizes simple equipment made of wood and stone. The exterior includes materials of steel, natural stone, and glass. They can be used as adhesives for wood, metal, glass, stone, and some plastics. The Romans also used cement, which reduced the variation of strength found in natural stone. It was a crudely cut triangular shaped stone of . Its facade is Baroque of light pink stone. There is disagreement as to the cause of the purple color of the amethyst stone. The building was clad in shingles with stone accents. The architecture consisted of rectilinear buildings made of mudbricks on stone foundations.