- a pencil
- some clear nail varnish
Put some scrap paper down (so you don't make a mess) and paint over the tip of the pencil with the clear nail varnish
Now leave it to dry. We recommend putting on a few coats of varnish!
You're all ready - now just wait for someone to try and use the pencil!
(And don't worry, a quick sharpening will make it usable again)