The vector's magnitude and direction is best understood when the dislocation-bearing crystal structure is first visualized without the dislocation, that is, the perfect crystal structure. In this perfect crystal structure, a rectangle whose lengths and widths are integer multiples of  (the unit cell edge length) is drawn encompassing the site of the original dislocation's origin. Once this encompassing rectangle is drawn, the dislocation can be introduced.
To comprehend the vector's magnitude and direction, it is helpful to first consider the crystal structure without any dislocations—i.e., the perfect crystal structure. In this structure, a rectangle whose lengths and widths are integer multiples of  (the unit cell edge length) encompasses the original dislocation's origin site. Once this rectangle is established, the dislocation can be included.