Sell fixed asset item

Hi all ,
is it right to sell fixed asset item and this item referred to an asset in Assets ??
because it is appeared in sales order and in sales invoice and i can sell it many times

You only see the Item code there but if you actually want to sell the asset, you need to do it from here

i know this but i add item and made it fixed asset and add it in assets but it appears in sales order
check PIC