"Dunsh" is a word for which there is no perfect equivalent in English. It means to jog or thrust in a violent manner; but those who know its proper application will see how feeble these meanings are. Jamieson approaches it when he says it is to "push as a mad bull." The proverb here means that they upon whom we depend can do with us as they please.
They may ken by your beard what ye had on your board.
They need muckle that will be content wi' naething.
They ne'er baked a gude cake but may bake an ill ane.
They ne'er gie wi' the spit but they gat wi' the ladle.
Or they never confer a small favour, or give a trifling gift, but they expect a greater in return.
They ne'er saw great dainties that thought a haggis a feast.
They're a' ae sow's pick.
Or all one kind—all bad alike.