fasten 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 down to (something)
To attach or connect something to something else. A noun or pronoun can be used between "fasten" and "down." Fasten that tile down to the floor before someone trips on it.
fasten up
To secure or close something, as by using buttons, zippers, etc. A noun or pronoun can be used between "fasten" and "up." It's freezing today, so be sure to fasten up your coat.
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.
fasten something up
to close something up, using buttons, a zipper, snaps, hooks, a clasp, or other things meant to hold something closed. Please fasten this up for me. I can't reach the zipper. Please fasten up my buttons in back.