With a little knowledge on how to use one, a marking gauge can help with many straight reference lines in the shop.
Marking and cutting gauges are precision tools that enable you to scribe lines parallel to the edge of your stock – typically up to about 6″ from the edge. A marking gauge uses a single round pin to score a line. There is an oversized style of marking gauge that enables you to scribe lines much farther from the edge of a board (from 12″ or so to several feet), referred to as a panel gauge. A marking gauge with two pins, that enables you to scribe both sides of a mortise simultaneously, is called a mortise gauge.
A cutting gauge uses a blade (with either a finger nail or pointed blade profile) or a round wheel (in which case the gauge is often referred to as a wheeled marking gauge). Japanese-style cutting gauges use a blade that has a tapered profile. You can also use a cutting gauge to rip thin veneer.
All these gauge designs feature a movable fence that rides along a stem, and can be locked in place with a knob. Some gauges feature an adjustment knob that enables you to fine-tune the position of the pin or blade.
Marking gauges are often made of wood, while cutting gauges, particularly those that use wheel cutters, are made of steel.
Like any cutting tool, these gauges work best when the pin, blade or wheel is sharp. Fortunately, most are quick and easy to sharpen.
Many woodworkers find that the pin of a marking gauge works best when scribing in the direction of the grain, while the blade of a cutting gauge scores a cleaner line across the grain. Both types of gauges will work in both instances if you’re careful.
Gauges are easier to control if you tilt the beam so that the marking pin or cutter blade cutter is at an angle to the registration line on your stock.
Scribed lines can be difficult to see, especially on darker woods. Use a sharp pencil to darken the scribe line before starting your joinery work.
If you do a lot of precision work, then opt for a gauge that has a micro-adjuster, which makes it much easier and quicker to fine tune your setting.