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Builders line bricklaying

Updated: October 2026

You have watched a bricklayer pull a line along a garden wall and assumed the vial keeps the courses straight. Builders line bricklaying works the other way round. The corners, called leads, are gauged, levelled and plumbed first. The line is a straight-edge between them. A hanging vial only checks that the two leads match. It does not set the gauge or plumb the quoin. The patio sequence is on [how to use a string spirit level](/hub/measuring-and-marking-tools/string-spirit-level/sub/string-spirit-level-how-to-use). The packs are on the [string spirit level comparison](/hub/measuring-and-marking-tools/string-spirit-level). UK bricklaying guides, read on 16 October 2026, are the source. A purchase through our links can earn a commission at no extra cost to you.

You have watched a bricklayer pull a line along a garden wall and assumed the vial keeps the courses straight. Builders line bricklaying works the other way round.

Our top picks

Presch Presch 2-piece line spirit level

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Presch Presch 2-piece line spirit level
8.1/10about £11.99
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Bubble Levels Bubble Levels 7-piece hanging line level

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Bubble Levels Bubble Levels 7-piece hanging line level
7.3/10about £5.99
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LSGZJZY LSGZJZY nylon line kit with 5 line levels

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LSGZJZY LSGZJZY nylon line kit with 5 line levels
4.8/10about £10.39
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On this page
  1. 1.The line is not the level
  2. 2.Gauge, then the arris
  3. 3.Pins, blocks, and a gap
  4. 4.A tingle when the span dips
  5. 5.When this page is the wrong job

The line is not the level

A lead is the stepped corner, built before you run the middle. BuildWiz and a UK training sheet put a long spirit level on that lead: level along the course, plumb on the quoin, and a gauge so each bed lands in the same place. The line goes on after those corners exist. If you hang a vial and lay to the bubble, you have skipped the part that keeps the ends upright. You want line, pins or corner blocks, a long level, and a way to mark 75 mm. The vial can wait until both leads are standing. It will not show a leaned quoin. If the wall is structural, retaining, at height, or beside an excavation, and you are not competent to build it, stop.

Gauge, then the arris

UK metric gauge, as BuildWiz and the training sheet use it, is a 65 mm brick plus a 10 mm bed, so 75 mm from one brick top to the next. Four courses come to 300 mm. Mark that on a gauge board and transfer it to both leads. Stay with 65 plus 10 unless your bricks are a different stated size. The line sits on the top front arris, where the face meets the top, of the course you are about to lay. BuildWiz leaves about 1-2 mm of daylight so the brick does not touch the string. Get the gauge wrong by a few millimetres at the lead and the error repeats every course. The vial cannot see that. Which spare pack to buy, if you want one at all, is on best string spirit levels.
Presch Presch 2-piece line spirit level

Testsieger

Presch Presch 2-piece line spirit level
8.1/10about £11.99
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Pins, blocks, and a gap

Line pins go into a perpend once that joint has hardened. BuildWiz says not to drive a pin into the wet bed you are about to load, because the pin moves and the line moves with it. Corner blocks grip the corner once the lead will hold them. Pins suit the first course. Blocks suit the courses after the corner can take a clamp. The 1-2 mm gap is the discipline in the middle of the wall. One brick pushed into the line bows it, and every brick after follows the bow. Pull that brick back. Do not hang a vial on the bowed string and call the bubble a correction.

A tingle when the span dips

On a short wall the line may stay straight. BuildWiz treats about 4 m as the point where sag shows, sooner in wind. About 25 mm of sag over 30 m is that source's rule of thumb, not a tolerance to build to. A tingle plate sits on a brick you have already checked. Rhinobuild sells one at about £4, 115 by 50 mm and 1.5 mm, zinc plated. If the leads are out of level, fix them with the long spirit level.

When this page is the wrong job

Stop if the wall retains soil, carries a load, or needs foundations you have not designed. For a garden wall you understand, gauge and plumb the leads, then run the line on the arris with a small gap. The hanging vial is optional after that. Where a vial belongs in the buying order is the string spirit level buying guide. A datum or a fall is a different instrument from the line between two leads.

Common questions

Do I hang a spirit level on the brick line?
You can, once both leads are built, as a check that those two ends match. You do not hang it to create the courses. Gauge, level and plumb come from a long spirit level and a 75 mm gauge on the leads. The hanging vial does not know whether a quoin is upright. Many bricklayers never put a vial on the line at all.
Where does the line sit on the brick?
On the top front arris of the course you are about to lay, with about 1-2 mm of daylight so the brick does not touch the string. The arris is the corner of the face and the top. If the line sits back from the face, you lay a straight top and a wandering face. If the brick pushes the line, the bow becomes the next brick.
What is 75 mm gauge?
It is one UK metric course: a 65 mm brick plus a 10 mm mortar bed. Four courses make 300 mm. Mark both leads from the same rod. A hanging level cannot see a bed that is 8 mm on one end and 14 mm on the other. If your bricks are not 65 mm, use that size plus a consistent bed.
When do I need a tingle?
When the span is long enough to dip. BuildWiz puts that at about 4 m as a practical limit, sooner in wind or with polyethylene, and says many shorter walls need no tingle. The plate rests on a brick you have already proved. About 25 mm of sag over 30 m is the same source's rule of thumb, not a measurement of your wall.
Pins or corner blocks?
Pins for the start, driven into a hardened perpend, not into the wet bed you are loading. Corner blocks once the lead will hold a clamp, so you are not making a hole in a joint that has not gone off. A pin in fresh mortar moves when you tension the line, and the courses after it follow that movement.

Related pages

String spirit level or a laser level

String spirit level

Best string line level UK: match the listing to the job

String line level buying guide: job before the pack

How to use a string line level: taut line, one vial

Sources

Public UK sources and the amazon.co.uk listings in the research digest, checked on 16 October 2026. Shelf prices can change.

  1. Approved Document H: drainage and waste disposal (retrieved 16 October 2026)
  2. Consumer Rights Act 2015, section 22 (retrieved 16 October 2026)
  3. Stanley 80 mm line level 0-42-287 (retrieved 16 October 2026)
  4. BS 958:1968, precision spirit levels (retrieved 16 October 2026)
  5. BuildWiz: builders' line (retrieved 16 October 2026)
  6. HSE: slips and trips in construction (retrieved 16 October 2026)
  7. Johnson Level: line levels (retrieved 16 October 2026)
  8. amazon.co.uk: string line level (retrieved 16 October 2026)