Templates for the clay brick firebox liner are cut and numbered. Patterns are made from fire brick units that are consistently shaped and easily identifiable during production. Later, the fire brick templates will be used to scribe clay brick which will compose the finished surface of the firebox liner. Liner bricks are cut on parallel angels to maintain the correct narrowness of head joint through the entire bed depth of the brick. This will prolong the life of the clay brick liner by preventing head joints from opening up and causing accelerated attrition.