This is a cheeky one. Of course you all know the difference between these two lovely words. But I like them, and it’s my blog, and you never know who might look things up (even “mandrel or mandrill” is quite popular).
An aglet is the little tube that you find on the end of your shoelaces, usually made of plastic but sometimes of metal. Sweetly, it apparently comes from the French for “little needle”, even though it doesn’t really look like or act like a needle in itself, but is used to help you thread the lace through the holes.
A ferrule is the little plastic or rubber cap that sits on the end of a walking stick or umbrella and prevents it from getting damaged.