Tape Measure: Curved Steel Blade, Spring and Case

The blade of a tape measure is a thin metal ribbon with a curved, concavo-convex cross-section when it is out of the case, which keeps it stiff, but it lies flat as it winds into a coil inside. The ribbon is painted, printed with its graduations and then given a polymer coat against wear, applied by a roller and cured in an oven. An internal coil spring winds the blade back onto its reel. The end hook is riveted through oval holes so it can slide by its own thickness, giving the same reading whether you hook it on or push it against something. Cases have been moulded in ABS since 1963.