Spirit level with magnetic (600)

That figure is the reason to choose this line over an unrated level, and it is worth knowing how to use it. Half a millimetre per metre is the tolerance the tool contributes. Over the 600mm of the level itself that is a third of a millimetre, which is invisible. But error accumulates across a job: set a four metre run of units by stepping the level along, and the tool's own tolerance can contribute a couple of millimetres of fall from one end to the other. Knowing that is what tells you when to step a short level along and when to fetch a long one or a laser — a decision most people make by instinct and occasionally get expensively wrong.

The frame is heavy duty aluminium at 1.5mm wall thickness, and thickness is what keeps a level honest. A thin-walled level sags very slightly under its own weight and flexes when you press it against a surface, and a level that bends reports the bend. Wall thickness is the least glamorous specification on a level and one of the most important.

Three vials give 90, 180 and 45 degrees. Anti-shock end caps protect the ends, which is where levels are almost always damaged — the end hits the floor and the shock runs straight into the vial housings, which is how a level ends up reading wrong while looking perfect.

It is magnetic, holding itself to steel sections, pipework, ducting and machine frames so both hands stay free.

The buyers are carpenters and joiners, kitchen and shopfitting installers, masons and bricklayers, plumbers and HVAC technicians, electricians, machinery installers, and hardware dealers supplying building and installation trades.

Two habits worth keeping. Check it end for end before trusting it on anything important: read a surface, mark the bubble, reverse the level in exactly the same spot, and it should read the same. Any difference means the vials have moved. And read the bubble from directly above rather than at an angle, because the viewing angle shifts its apparent position — a small error, but one you repeat at every step along a long run. Ask on WhatsApp for a price.