Am I the only one who didn't know about this?
Your emery board contains several layers. When it starts getting old and dull, you can peel off that layer and reveal a fresh emery board underneath. Neat, right?
Now you can shape your mani without any worries.
Of course, this does mean that I've been throwing out perfectly good emery boards for years.
Sigh. Oh well.
Be sure to pass this hack on to any friends who might not know. It could save them some money in the long-run.