· Because the edge type jog MN can't move by glide, the moving screw dislocation trails an edge type dislocation dipole OMNP, as illustrated.
· OM and NP are separated by a single lattice plane and the dipole OMNP is, therefore, either a row of vacancies or a row of interstitial atoms depending upon the location of the half planes associated with the edge components OM and NP.

· Work for the creation of these point defects (about 1eV per defect) comes from the external forces and contributes to the work hardening.