A line level is a specialized tool used to ensure a straight line is perfectly horizontal or vertical. It’s often
used in construction, woodworking, and other trades where precision and accuracy are essential. It is simple yet
indispensable tool for maintaining straight lines and ensuring accuracy in various projects.

Line Spirit level:

• Line levels (or ‘string’ levels) are a special spirit level used for levelling across longer distances. Hanging
  on string.
• An instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). Used on building
  sites for measuring over a long distance. Must be in center of line.