A marking gauge is used to score a line parallel to the edge of a piece of wood. A small metal spike is set on the wooden shaft with an adjustable stock, which slides up and down it. The stock is set at the required distance from the spike. The face of the stock is then pressed firmly against the edge of the timber and the tool is pushed away from you to scribe the line.
Remember the old adage “Mark twice, Cut once”
A similar gauge, a cutting gauge, is used to cut across the grain of wood. If you tried to scribe a line with a marking gauge here, the spike would tear the wood’s surface. In place of the spike, a sharp blade is held in the shaft with a removable wedge.
A third type of gauge is known as the mortise gauge. This has two pins, one fixed and one moveable for marking the parallel sides of mortise and tenon joints.
Remember, when you measure and mark wood, always do so on the face side or face edge – the best looking side or edge of a piece of timber. Professional carpenters use a looped letter ‘I’ for the best side and a small ‘x’for the best edge.