I found the following sentence in this link and I'm having a hard time understanding the meaning of it.
"Line mattress and pillows if you are allergic to dust mites"
What does it mean to line a mattress or a pillow? I have found two possible definitions in this context for the verb "line", but I don't think either one of them is the "exact" definition in this case:
- To fit a covering to the inside surface of.
- To cover the inner surface of.
(The inside or the inner surface of a matress or a pillow?)