From Longman Dictionary of Contemporary Englishhard-and-fastˌhard-and-ˈfast adjective [only before noun] clear, definite, and always able to be used It is impossible to give hard-and-fast rules, but here are some points to consider.
Examples from the Corpus
hard-and-fast• Similarly, it is not possible for him either to give a hard-and-fast definition of Truth.• There is no hard-and-fast divide between water-breathing and air-breathing animals.• Clearly there are dangers involved in drawing a hard-and-fast line between the two principles of participation and identity.• Mrs. Bottomley With respect to my hon. Friend, I do not believe that it is ever possible to cut a hard-and-fast line.hard-and-fast rules• The school doesn't have any hard-and-fast rules about what children should wear. 