Grammar question

I thought a sentence cannot end with "for".

Were you taught that a preposition should never be placed at the end of a sentence? There are times when it would be rather awkward to organize a sentence in a way that would avoid doing this, for example:

in some passive expressions:

√ The dress had not even been paid for.

X Paid for the dress had not even been.

√ The match was rained off.

X Rained off was the match.

in relative clauses and questions that include verbs with linked adverbs or prepositions:

√ What did you put that there for?

X For what [reason] did you put that there?

√ They must be convinced of the commitment they are taking on.

X Of the commitment they are taking on they must be convinced.

There’s no necessity to ban prepositions from the end of sentences. Ending a sentence with a preposition is a perfectly natural part of the structure of modern English.