Simplify the following text for a Grade 2 native English-speaking person.
Original: A doorstop ( or door stop ) is an object or device used to hold a door open or closed , or to prevent a door from opening too widely . Alternatively , a doorstop can be a thin slat built inside a door frame to prevent a door from swinging through when closed .
Simplified: A doorstop ( or door stop or doorstopper ) is a tool .