Sandpaper is a rough paper with sand or small bits of rock on it. People use it to make wood smooth or to take off old paint.
Sandpaper can make people think of fixing things or making things better.
Examples:
I need sandpaper to make this wood smooth.
The sandpaper is rough and scratchy.
She used sandpaper to take off the old paint.
I don't like the feeling of sandpaper on my skin.
He used sandpaper to make the wood as smooth as glass.
The sandpaper made the wood feel nice and smooth.