Babies chew. Its what they do, and we were suprised to learn how productive that chewing can be the day we ran our hand along the edge of a used crib at a garage sale and came away with splinters.
We recently saw a Gummi Crib Rail in action, and they really are a great safety measure for babies that chew. Some cribs come with built in teething rails now, but most don't, and we have often wondered how safe it is to be chewing on the unprotected wood edges of crib rails.
Gummi Rails are 50" long and can be trimmed to fit most cribs. The site states that they take 10-15 minutes to install, but we asked someone who did install them on an older crib and our field reporter says 30-45 minutes to do the actual install - longer than advertised, but still a reasonable amount of time to us.
They are opaque, but keep in mind that installing these will mute the colour of your crib rails, and we would like to see what they look like on a darker-finish crib. However, most safety related baby items aren't necessarily designed for looks, and for $14.95, Gummi Rails look like a good investment for a chewy baby.