Header
It is a full brick or stone that is laid along with its length perpendicular to the face of the wall. This implies the end of a brick as seen within the wall face measuring 9 cm.
Stretcher
It is a full brick or stone that is laid with its length parallel to the face of the wall. The side of a brick has seen in elevation in a wall, while the brick is laid flat measuring 19 cm × 9 cm.