The term 'CERTAIN BOLT HOLDER' is a job description for a TNUT, which stands for Threaded Nut. A Threaded Nut is a type of fastener that is used to secure two or more objects together. It is typically made of metal and has internal threads that are designed to fit with the external threads of a bolt or screw. The Threaded Nut Holder is responsible for ensuring that the nuts are properly secured and tightened to the bolts. They must also be able to identify any potential problems with the nuts and bolts, such as corrosion or wear and tear.