Public Notice in Library

??don't occupy seats by any items

I don't understand the above. Please explain it using different words.

Like you put some books or belongings there in advance and you can come back having that seat any time after. Sometimes all seats are occupied by books but no one even been there.

and it is an exercise from my translation class. That sentence is a direct translation I did, but I find hard to make it natural in English........

Try,
Do not place books or other items on seats to occupy them.