A laser level emits a straight laser beam, usually a flat plane of light. This can then be mounted on a tripod or surface and used as a guide during construction. A common use of this tool is in the levelling of land, ensuring a consistency across a surface. This may be in the case where a surface needs to be flat horizontally, or needs to be sloped at a consistent angle.
Some have said that this is essentially a modern version of using a taut string tied between stakes, and of the pantheon of construction equipment may be considered a tool of moderate worthiness.