2. Hand-held instruments

So-called "hand-held" instruments are used for various length measurements directly by hand, i.e. without a support or length reference, as in the case of comparative measurements with a marble. Good practice dictates that these instruments should be used with a light, relaxed hand, since, particularly with slide instruments, the measuring effort exerted by the operator can have a significant influence. This influence is significantly reduced with micrometer screw instruments fitted with a torque-limiting device, which allows zeroing on the standard and measurement with the same effort.