A torpedo level is generally a 6 to 12 inch-long level in the shape of a torpedo. The levels can be used to see if something is plumb or level. Some torpedo levels use a vial of liquid. Others use lasers to tell you if something is straight. Some will allow you to check multiple angles at once. To use the level, align it with the edge of an item you are checking and hold it until the bubbles or laser settle.