"Watch your head on the shelf" or "Watch the shelf over your head""

[slmhlm]

hello,

1 "Watch your head on the shelf"
or
2 "Watch the shelf over your head".

I heard that 1st is correct. but logically "head on the shelf" is little bit awkward.

What do you think?
Are there any examples like this in English?

Thank you,

[Mr Greg]

It depends on the context.

I would use (2) if the person is not aware of the shelf. (1) if the person is aware of the shelf.

Though I would always use (2) personally.