By using the finite element method, the dynamic stress caused by vertical contact impact between bolt locking surface and barrel extension locking surface of a new rifle was studied.

Then vertical contact dynamics of tire is analyzed with contact patch considered, and that of the system composed of wheel, suspension and car body are analyzed by using modal synthesis method.

The key to Silent Feet is slowly and simultaneously to contact the wall's vertical plane and the foothold's horizontal aspect - so visually track the movement.