A silver hammer breaks an iron door.
More French Proverbs:
Every one has a fool in his sleeve.French
Half figs, half raisins.
French
Half figs, half raisins.
French
When the kitchenmaids are together the roast burns.
French
He has great need of a fool who makes himself one.
French
If you wrestle with a collier you will get a blotch.
French