I have had many occasions where purchaser clients arrived at their new home to find it full of items that the vendor left behind; most recently, a buyer client of mine agreed to allow the seller to leave behind a boat that couldn’t be moved because of the weather, which was only removed the very last day the seller was permitted to leave it there. (And the seller left behind some junk along with the boat, that he conveniently forgot to remove when he picked his boat up.) As a seller, you can only leave items if you have specifically agreed to do so in your agreement of purchase and sale. This includes construction materials; though it is easy to assume that the buyer would want leftover paint or trim, if the buyer doesn’t want it, you could be on the hook for the cost of removal after closing. If you aren’t sure, ask – before closing.