Setting out with a laser level

Learn to use a self-levelling laser level to mark accurate, dead-level reference lines before any DIY job.

SL-01Understand what the laser doesA laser level shines a straight, level line of light onto any surface it hits, so you don't have to guess a level line by eye. Most are 'self-levelling': an internal pendulum settles the beam automatically once you switch it on and stand it roughly level. This guide covers line lasers, which project a long straight line - point lasers just project single dots and are used differently.

SL-02Set the laser on a stable baseStand the laser on a tripod, a stack of flat boxes, or any solid surface - it will fine-tune itself once switched on, but it can't cope with something that moves or wobbles. Switch it on and wait a few seconds while the pendulum locks and the line steadies. The common beginner mistake is propping it on something unstable, like a stepladder someone might knock, which throws the line off without you noticing.

SL-03Position it at the right height and distanceDecide what height you need the line at - for example, the top edge of a run of kitchen units or a horizontal guide for tiling. Set the laser up roughly there, then check where the line actually falls using a tape measure at two points. Move the laser up or down until the line sits exactly where you want before marking anything.

SL-04Mark the line - don't just follow it by eyeUse a sharp pencil to put small marks on the wall every 300-500mm along the projected line, rather than trusting the visible beam alone. Laser lines fade in bright light and can look slightly different depending on the angle you're standing at, so pencil marks are your permanent, reliable record. The classic beginner mistake is drawing one continuous freehand line 'following' the laser, which brings back the same wobble a hand-drawn line always has.

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SL-05Join the marks with a straightedgeConnect your pencil marks using a straightedge or spirit level, not freehand, to get one crisp, dead-straight line. This final drawn line is what you actually cut, drill or fix to - the laser was only ever there to give you accurate points to join up.

SL-06Know the mistakes that catch people outBright sunlight or a well-lit room can make the laser line almost invisible, so work in dimmer light or shade the area if you can. Always lock the pendulum before moving the laser between jobs - carrying it unlocked can damage the levelling mechanism and quietly ruin its accuracy from then on. Give the laser a knock-check occasionally too: a drop or bump can throw off its calibration with no obvious sign that anything's wrong.

SL-07Check you've actually got it levelMeasure from the floor, or another fixed reference point, up to your marked line at both ends and in the middle. All three measurements should match within a couple of millimetres. If they don't, something moved while you were marking, or the laser wasn't properly level to start with - redo the setup rather than trusting a line that doesn't check out.

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