The term 'CERTAIN MASON' is a combination of two job descriptions. The first part, 'CERTAIN', is an adjective meaning 'DEFINITE' or 'SURE'. The second part, 'MASON', is a noun referring to a BRICKLAYER, someone who works with bricks and mortar to construct walls and other structures. A BRICKLAYER is a skilled tradesperson who is responsible for laying bricks, blocks, and other masonry materials to create structures such as walls, patios, and chimneys.