Torpedo Level - Best Tools for the Weekend Warrior - DIY Essentials - Bob Vila
Pro Tool Reviews
The sealed vials of the torpedo level contain water, alcohol, or another clear liquid and an all-important air bubble. Each tube or vial is slightly curved and has two parallel lines drawn at its center. When the bubble is aligned between the hairlines, it indicates that the object being trued is perfectly vertical or horizontal, depending on the orientation of the vials and how the level has been placed on the object.