• The mortar joint connecting two bricks horizontally is usually met by the flat side of a brick atop and below it.bricks image by Bosko Martinovic from Fotolia.com
  
  Bricks are blocks of heavy material, usually clay, laid on top of one another to form walls, columns, chimneys, decorative accents and other structures. Masons join bricks using mortar, which hardens and forms an uninterrupted surface with the bricks. An object as basic and essential as a brick has invited numerous variations over its centuries of use.
  
  

Pressed Clay Bricks

• Most bricks are made from kiln-baked mixtures of clay. Usually, when you see a building facade made of even rows of dark red bricks, those are clay bricks. Pressed clay bricks have "frogs," or recesses, on each of their bedding surfaces.
  
  

Wire-Cut Clay Bricks

• Wire-cut bricks have been cut into shape by a wire. They can usually be identified by three or four holes going through the brick. These holes constitute about 25 percent of the brick's volume.
  
  

Glazed Brick

• Glazed bricks are like ordinary clay bricks, except that the exterior surface has been coated with a white or colored ceramic glazing. These bricks are laid in places like hospitals and laboratories which require sanitary conditions. Their ceramic glaze facilitates ease of cleaning.
  
  

Sand-Lime Brick

• Sand-lime bricks are not made of clay, but rather from a mixture of slaked lime and fine sand. They are mechanically molded and hardened under steam pressure. German and northern-European structures make extensive use of this brick.
  
  

Clinker Bricks

• Clinker bricks have been heated in the kiln to much hotter temperatures than other bricks. Under such heat, the pores in the brick actually melt and fuse shut. The result is a very dense, heavy, water-resistant and durable brick. Clinker bricks also tend to be more irregularly shaped than other bricks.