Oh, The guitar necks? Certain type of wood is sesitive to humidity (high humidity or lack of it). The oil protects the wood from drying up, or...the opposite. I have to do it every six months or so. Keeps me busy, 'cause nowadays I have about 15 guitars.
That's why I like synths - all they need is a battery replacement about every...thousand years !
_________________________ A gentleman is one who never hurts anyone's feelings unintentionally. - - - Oscar Wilde