A line laser level is a tool used in construction and carpentry to project a straight line of laser light across a surface. This helps ensure that surfaces are level and aligned accurately, making it easier to install items like shelves, tiles, or framing. The laser creates a visible line that can be seen over long distances, providing a reliable reference point. These devices come in various types, including self-leveling and manual models. Self-leveling line laser levels automatically adjust to maintain a level line, while manual models require the user to adjust the angle. They are essential for achieving precision in various projects.