Green’s Dictionary of Slang

knocker n.2

[ety. unknown; ? link to Yid. naches, pleasure]

(Aus.) common sense.

[Aus]H. Lawson ‘Two Larrikins’ in Roderick (1972) 231: The old woman might have had the knocker to keep away from the lush while I was in quod.
[Aus]Bulletin (Sydney) 2 Aug. 16/4: In ’83 or ’84 13 men started overland from W.Q. with a few horses and very little capital but plenty of what they called ‘knocker.’ At every station they struck they demanded rations, and if police had been more plentiful in that part they would never have reached Kimberley.

In phrases

off one’s knocker (adj.)

(Aus.) mad, insane, uncontrolled.

[Aus]E. Dyson Fact’ry ’Ands 201: Fuzzy continued caperin’ [...] clean off his knocker, ’n’ pickled in misery.
put the knocker on (v.)

(Aus.) to call a halt, to forbid.

[Aus]M.B. ‘Chopper’ Read Chopper 4 155: My old Dad put the knocker on it [i.e. a proposed assassination] with a passionate verbal tirade.