I was asked by another farrier who couldn't get to this mare below to balance her out on her  hind end.  She was unshod on the rear and had worn of the outside of the hoof so much that she was lame and striking herself when she moved.  I shimmed up the outside which spread her feet apart.  After that the owner said she was going great, and the farrier had enough foot to trim and balance her out without the shim.