The Reshape tool is a specialized variation of the standard UV Copy tool; its chief application is in the sharing of UVs between morph target pairs.
Import Shape
Loads the source mesh into the same window as the already open target mesh. Its not the UVs that are copied from the imported source mesh, but its shape, and so the already loaded target mesh should have UVs already. The imported source mesh can be moved and rotated with the Space-MMB and Space-LMB hotkey actions.
Delete
Deletes the imported source mesh.
Transfer Shape
To transfer the shape of the source mesh over to the target mesh, first LMB select an edge on the target mesh, then MMB select an edge in the same relative position on the source mesh. When you have selected both edges, tap the space bar and the shape will be copied across. Note: Both meshes must have the same topology (i.e. the same number and arrangement of polygons) for this to work.
50 / 50
Also transfers the shape, but creates a 50/50 blend between the source and target meshes. This can be used to develop UVs that minimize distortion across both shapes.
