Levels

For: Precision carpentry across a long expanse, as when installing cabinets, trim, doors, or floors. Plastic models are suitable for rougher work on gutters, drains, concrete slabs, and masonry walls.
How it works: Lengthy tool can span long distances, unaffected by bumps and dips. Curved vials are more accurate, but only the bottom one in the pair indicates level at any given time.
Shown: Crick Tool Co. 48-inch wood level; about $120; cricktool.com