Fit two nuts on the other side, loosely, and then tighten them against each other so they operate as jam nuts. Then, with a spanner holding the inner jam nut in place, undo the lock nut you're trying to shift. Once it's off, loosen the two jam nuts and unthread them.
Fit two nuts on the other side, loosely, and then tighten them against each other so they operate as jam nuts. Then, with a spanner holding the inner jam nut in place, undo the lock nut you're trying to shift. Once it's off, loosen the two jam nuts and unthread them.