Comment by dangerbird2

I think GP's use of "hand-clocking" to refer to the factthat the z80 can run on a very low clock rate, to the extent that you can have a hand switch that sends individual clock pulses to the processor. This can be useful for testing purposes as well as for low power operation in embedded applications.

http://www.thomasloven.com/blog/2013/01/Z80-Tester/