What should I mark with — and how do I mark something a pencil will not show on?

The marker decides how fine your line is and whether you can get rid of it afterwards, and both matter. A soft pencil line on oak is 1.5mm wide and soaks into the grain; a permanent marker on a worktop is permanent; and a knife line on a piece you were going to leave unpainted is a cut you cannot sand out without losing the surface.

Step by step

1. Ask whether the mark will be seen in the finished work.If the marked face will be visible and unpainted, a knife line is a permanent cut and a soft pencil is a stain in the grain. Mark on the waste side, or on a face that will be hidden.
2. Match the line width to the tolerance.A carpenter's pencil line is over a millimetre wide, which is fine for a stud position and hopeless for a mitre. Use the finest marker the job's accuracy actually requires and no finer.
3. Sharpen a pencil to a chisel, not a cone.A chisel point held against a square gives a consistent line right up to the blade, and it stays usable as it wears. A cone point rolls, wanders and puts the line a variable distance from the square.
4. Use tape on anything that will stain.Tiles, glass, worktops, painted walls, powder-coated metal. Mark on the tape, work through it, peel it off. Nothing to remove and nothing to explain afterwards.
5. Use a chinagraph or a silver pencil where graphite vanishes.Dark oak, walnut, slate, black composite, galvanised steel and anything wet. Graphite on a dark surface is invisible under a work light, which is where most of these mistakes get made.
6. Mark the waste, not just the line.A small cross or a squiggle on the waste side of every line. It costs a second and it prevents the entire class of error where the cut is made on the wrong side of the mark.
7. Never use a permanent marker on anything you will not cut away.It bleeds through paint, through primer, and out of end grain months later. If you must use one, keep it to the offcut side of the line.
8. Keep the marking tools separate from the general toolbox.A knife blade with a chip in it and a pencil sharpened by a saw both produce bad lines. A small tin with a knife, two pencils, a sharpener and a roll of tape is worth having.

Tips

• For marking a hole centre on metal or plastic, a centre punch is the marker — it makes a dimple the drill point cannot wander out of.
• On wet ground and wet timber, a carpenter's pencil still writes where a marker will not. Wax-based markers also work on damp surfaces.
• Chalk marks brush off in the rain and off anything you brush against. For exterior setting-out that has to survive overnight, use a spray marker paint or drive a nail.
• Silver pencils are also excellent on dark plaster and on the reverse of plasterboard, where a normal pencil is genuinely hard to see.

Common mistakes

• Using a permanent marker on timber that will be painted — Marker pigment bleeds through emulsion and even through some primers, reappearing weeks later as a grey ghost line. Use a stain-blocking primer if it has already happened.
• Marking a fine joint with a blunt pencil and then cutting to the middle of the line — The line has a width, and choosing its middle is a guess. Either mark thinner or decide in advance which edge of the line you cut to and be consistent.
• Knife-marking a visible surface — The cut does not sand out without taking the surface down with it. Mark the waste side, or use a pencil on show faces.

Alternatives

• HB or H pencil, chisel-sharpened: The general answer for timber. Sharpen the lead to a flat chisel shape rather than a cone, so the line stays thin as the point wears and you can hold it hard against a square. An H or 2H stays sharp longer on softwood; anything softer than HB is a wide, smudging line.
• Marking knife: For anything that will be cut to a joint. A knife line is a fraction of a pencil line in width, it severs the surface fibres so the cut edge stays clean, and it gives a chisel a physical wall to drop into. Not for pieces that stay unfinished where the cut would show.
• Carpenter's pencil: Flat, tough lead, sharpened to a broad chisel with a knife. Right for structural timber, masonry, rough sawn stock and anything dusty. Too coarse for joinery and unable to reach into a corner.
• Mechanical pencil, 0.5 or 0.7mm: A consistently fine line with no sharpening, which suits sheet goods and careful layout work. The lead snaps on rough grain and it is fiddly with gloves on.
• Chinagraph or china marker: A waxy crayon that writes on glass, tile, metal, polished stone and wet surfaces. Wipes off most non-porous materials with a cloth. The line is wide, so it marks where rather than exactly where.
• Silver or white pencil: Shows clearly on dark timber, slate, dark laminate and black steel where graphite disappears. Available as ordinary pencils and as mechanical ones with replaceable leads.
• Scriber or scratch awl: For metal, where a permanent, very fine line is wanted and the surface will be cut or filed anyway. Never on timber — it tears the fibres and follows the grain.
• Masking tape as a marking surface: The universal answer for anything that must not be stained. Run tape along the line, mark on the tape, cut through it, and peel. It also reduces chipping on tile and laminate, so it earns its place twice.

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