Ni chair ni poisson = Neither fish, flesh, nor fowl.
Chaise
Être assis entre deux chaises = To fall between two stools. (See [Chasser].)
Chambre
Il y a bien des chambres à louer dans sa tête = He is an empty-headed fellow.
Chameau
Rejeter le moucheron et avaler le chameau = To strain at a gnat and swallow a camel.
Champ
Il est fou à courir les champs = He is as mad as a March hare.