Levels for construction have come a long way from the early days of the weighted string and the two bits of wood that were popular with the builders of the pyramids. Fourteenthcentury craftsmen used fluids to find level references — either with a water level or a bubble in a slightly bowed glass tube filled with liquid and attached to a straight rail. More recently, levels were made of exotic hardwoods bound in brass with bubble vials set in putty in a recess in the rail. Dimensionally stable species like mahogany, ebony, and rosewood were popular, though today many levels are machined out of aluminum box beams. Here are a few companies that have taken level technology one
