(fastens, fastening, fastened)
1.
When you fasten something, you close it by means of buttons or a strap, or some other device. If something fastens with buttons or straps, you can close it in this way.
She got quickly into her Mini and fastened the seat-belt...
Her long fair hair was fastened at the nape of her neck by an elastic band.
...the dress, which fastens with a long back zip.
= do up
VERB: V n, be V-ed prep, V prep, also V n prep
2.
If you fasten one thing to another, you attach the first thing to the second, for example with a piece of string or tape.
There were no instructions on how to fasten the carrying strap to the box...
= attach
VERB: V n prep/adv
3.