prepositions - What differences are between "at the end" and "on the end"?

I am familiar with " at the end" and " in the end" constructions, but I have found in "English Grammar in Use" book, the following sentences that contain "on the end":

1. Question tags are mini-questions that we often put on the end of a sentence in spoken English.




2. Put a question tag on the end of these sentences.

Naturally, I would have used at instead of on.

What differences are between "at the end" and "on the end"?

Thank you!

Answer

In general "at the end" is more natural. (For example, "In German the verb often comes at the end of a clause.") It seems to me that they have used "on the end" here because the question tag is something extra that you ADD ON. You could even use "onto" in this specific context.