Salt water's the very thing for those little knocks.

Standing there listening attentively, he presently heard three little knocks given, as by a hand on the door.

You should bear in mind that I hinna your cleverness' (they were constantly giving each other little knocks).

The tapping continued for half a minute or more- aseriesof hurried, gentle little knocks as from a child's smallest finger-tip

I will give two little knocks on the panel, I will awake him, and we will explain matters before he can move.

For my agreement had been to give one loud knock (if you happen to remember) and after that two little knocks.