  In this study of the Reidemeister moves within the classical knot theory, we
focus on hard diagrams of knots and links, categorizing them as either rigid or
shaky based on their adaptability to certain moves. We establish that every
link possesses a diagram that is a rigid hard diagram and we provide an upper
limit for the number of crossings in such diagrams. Furthermore, we investigate
rigid hard diagrams for specific knots or links to determine their rigid hard
index. In the topic of shaky hard diagrams, we demonstrate the existence of
such diagrams for the unknot and unlink, regardless of the number of
components, and present examples of shaky hard diagrams.
