Since the discovery of carbon nanotubes their unique electronic and mechanical properties are finding promising applications in nanometer size electronics and mechanics. We consider a set of nanomechanical devices where the relative motion of nanotube shells is controlled by potential relief of intershell interaction energy. Two-shell carbon nanotubes with potential relief corresponding to the bolt and nut pairs are studied.The classification of two-shell nanotubes with commensurate shells is also proposed.The barriers for relative motions of shells along the helical line of thread and for jumps to neighbour helical line are studied as functions of shell lengthes. The Fokker-Planck equation of relative motion of carbon nanotube shells along the helical line under the action of external forces (fields) is derived. Two promising types of conversion the force applied on the shell into relative rotation of shells are found. The first type is the conversion of the external force directed along the nanotube axis into the relative rotation of shells. In this case the two-shell nanotube can operate as a nanowhirligig or even as perforating nanodrill if the applied force frequently change its direction. The second type is the conversion of external force moment applied on the shell into the relative motion of shells along the nanotube axis. In this case the rotation of shell results in its extension as in a glue stick.It can be used for nanoswitch.