Wot's a witness spike?
The little upside-down cone thingy that hangs off the bottom of the Xmsn inside a ring of softer metal which is on the work deck. If the Xmsn gets a big rock up, the spike dings against the metal and deforms it, and is evidence of a "spike knock", i.e. hand over your cheque book, sonny, this is gonna cost ya.
Looks like he lost the tail
Eh???