After applying a protective layer, be sure there are no faults or discontinuities that expose the substrate beneath. Small patches of weak or missing coating, known as 'pinholes' or 'holidays', can become corrosion foci, significantly reducing the life of a protective coating system. A pinhole or holiday detector is a non-destructive equipment that detects discontinuities in a coating system, such as holidays, pinholes, and cracks. Porosity detectors are also known as continuity testers, holiday testers, spark testers, and jeep meters.