If only a continuous distribution of edge dislocations is used to represent the opening of a crack by a prescribed normal displacement such that the body deforms in a plane strain mode, there is a corresponding transverse displacement of points on the crack surface; it is therefore impossible, with dislocations alone, to discuss situations where both the normal and transverse displacements are independently prescribed. The dislocation approach is therefore extended to encompass such situations, by super-imposing an appropriate distribution of body force along the crack plane.