Grooved Bricks

Brick was first made of clay, but by the middle ages, people had figured out that clay wouldnt hold up under pressure, so they started using mortar and other materials to hold bricks together. This led to a long history of brick-making that includes the grooved bricks that you might see in an old building. Grooved bricks are cut and pressed into a mold to make them round and create a groove down the middle of each one.