"Hypothes of rigid plane", as round shaft distorts, is expounded and proved by use of the elastic theory, thus providing the hypothesis with a theoretical basis and deepened concepts.

A shaft in the box and a box cover wheel without axial or radial clearance is another factor to move, should refer to a box of round renovation measures.

It is the middle of a slender wooden shaft with a hollow circle at both ends of each round, round a few weeks to open mouth square posts.