Do we use "do up" for belts as well like 'your button is undone'. Do it up.

[tufguy]

Do we use "do up" for belts as well like 'your button is undone'. Do it up?

Is it correct to say "your belt is undone. Do it up"?

 

[PeterCW]

In BrE we would be more likely to say "buckle it".

 

[Tarheel]

In BrE we would be more likely to say "buckle it".

That's it! However, If one adult is speaking to another adult then saying the belt is undone should be sufficient.

 

[emsr2d2]

Do we use "do up" for belts as well like in the same way we do in "Your button is undone. Do it up"?

Is it correct to say "Your belt is undone. Do it up"?

Note my changes above. You must remember to capitalise the first letter of a complete sentence in quotes.
Despite being a BrE speaker, like PeterCW, I've never used "buckle" that way. I would always say "Do your belt up".

 

[Skrej]

Unlike a button or zipper, it's far less likely for someone to go with their belt undone unnoticed. They're going to be reminded when their pants fall down!

I can't really imagine a scenario where I'd have to remind someone to fasten their pants belt, but if I did, I suppose I'd say "Buckle your belt" or 'Fasten your belt", the same as I do when talking about seat belts.