"hammered down" is a correct and usable phrase in written English.
You can use it in the context of an action that involves hammering down something, as in "He hammered down the nails in the wall".
"I shouldn't have got hammered down at the Danforth.
He hammered down the 100th ace of the tournament.
Even yet the rain hammered down on my old hotel at Killary.
As a hoary old Japanese saying has it, "the nail that sticks out is hammered down".
Japan".The nail that sticks up", runs a hoary Japanese saying, "gets hammered down".
In Japan, people say: "the nail that sticks up gets hammered down"—an engineer's view.
The rain hammered down as we headed off for our first meeting.
Maybe a more experienced team would have hammered down the lid.
Braka doesn't even lift his paddle and it's hammered down at £1.7m.
He looked weathered and hammered down, as if he'd spent his life doing manual labour.
His list of a hundred things to do had been hammered down essentially to one: get a paying client.
