PPT Slide
The most important one-dimensional, or line, defect is the dislocation.
Dislocation is the defect responsible for the phenomenon of slip, by which most metals deform plastically.
Therefore, one way of thinking about a dislocation is to consider that it is the region of localized lattice disturbance separating the slipped and unslipped regions of a crystal.
Line Defects - Dislocations