Copy Weightmaps from other Mesh objects rigged to the same armature.
Weights are copied from the closest vertices from other meshes. If 2 or more vertices are located at the same position, then it is not defined which weight will be transferred to the active Object.
If you want to copy weights from other meshes (weight sources) to a mesh (weight target), then all source meshes and the target mesh must be siblings of the same armature. (all meshes must be attached to the same armature). All currently selected bones will become Copy targets in that case.
Note: Only visible weight sources are taken into account. Hence at least one weight source (mesh) must be visible.
Note: If you want to do a full weight Copy, then you only need to select all SL Bones (the blue ones) as seen in the image to the right.
Note: Custom meshes can also be used as Sources for a Weight Copy, provided they are siblings of the active Mesh!
Note: the topology of the source meshes and the target mesh may be different!