What is a cross-line laser?
A cross-line laser is a measuring instrument that projects horizontal and/or vertical laser lines onto walls, floors, and ceilings. It replaces the spirit level and plumb bob in many situations: you can set out a perfectly level or plumb line over long distances without physically holding anything against the wall.
How does it work?
The cross-line laser contains one or more laser diodes that project a line (rather than a dot) through a lens or prism. A built-in pendulum or electronic self-levelling system ensures the line is automatically level.
Types
| Type | Lines | Application |
|---|---|---|
| Line laser (1 line) | 1 horizontal or vertical | Tiling, hanging pictures |
| Cross-line laser (2 lines) | 1 horizontal + 1 vertical | All-round DIY and construction |
| Multi-line laser | 3-8 lines, 360° | Professional, complete room layout |
| Rotary laser | Spinning dot = line around entire room | Large spaces, outdoor work |
What do you use a cross-line laser for?
- Hanging a kitchen — Horizontal line at the correct height
- Tiling — Reference line for the first row
- Installing window frames — Plumb line on the wall
- Setting out foundations — Height lines over longer distances
- Installing battens — Horizontal reference on the wall
- Decking/patio — Check height across the entire surface
- Ceiling cladding — Reference line for a straight ceiling
Accuracy
| Type | Accuracy |
|---|---|
| Budget cross-line laser | +/-2-3 mm per 10 metres |
| Professional | +/-1 mm per 10 metres |
| Rotary laser | +/-1 mm per 20 metres |
For DIY, a budget cross-line laser (+/-2 mm per 10 m) is more than sufficient.
Tips
- Self-levelling — Most cross-line lasers level automatically. If the laser is too tilted, it flashes as a warning.
- Outdoors — In daylight, the laser is difficult to see. Use laser glasses or a receiver.
- Do not look into the laser — It can damage your eyes.
Related terms
- Spirit level
- Plumb bob
- Diagonal measurement