Header – Heads form the visible course and the long, narrow side is viewed from a side cross-section. This is often used to interlock a double wall (two adjacent wythes). Rowlock – The long narrow sides are top and bottom; the heads visible. Single course. Above lintels. Between string courses. Occasionally the topmost course.Soldier – Used mainly for decorative purposes as its upright nature does not lend itself to the compressive strength of a masonry unit and tends towards inward or outward lean (where mortar is used) or stress in successive courses. The long, thin sides are visible; the heads are top and bottom.Sailor (rare) – Decorative, upright, weak and heat-permeable: The long thin sides are viewed from a side-cross section and the long thick sides are visible; the heads are top an