fasten down(redirected from fasten it down)
To attach or connect something to something else. A noun or pronoun can be used between "fasten" and "down." Fasten that tile down before someone trips on it. I fastened down the car seat, so it shouldn't budge at all.
fasten something down (to something)
to attach something down to something else. Fasten this board down to the top of the workbench. Please fasten down the board.