Notice in the photos that all of the block are stacked uniformly with the exterior sides of the block consistently placed. This allows the mason to pick up the block the same way every time, apply mortar on the head joints, and place the block in a bed of mortar.
At each corner of the building and on each side of every opening, Left Corner block and Right Corner block are placed adjacent to the Stretcher block. Openings also require half block to be stocked as well. Masons prefer to have the block supply stocked 5 or 6 block wide perpendicular to the ‘working wall’. Proper stocking of block would permit room between stacks to place a mortar board.