hand jive

If you've got a big servo coupled directly to the y-screw, how do you
hand crank the machine?

Is the only solution to use a servo w/ double ended spindle and fit
the hand crank to the other end? Well, wait, I guess one could fit a
spur gear on the end of the lead screw and use a geared hand crank
together with some kind of tumbler...

By now, after much painful trial and error, some standard practice
must have emerged in the CNC world. Can someone tell me what it is?

Thanks very much.

--Jack Williamson