hard-and-fast

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++ˌhard-and-ˈfast adjective [only before noun]  clear, definite, and always able to be used 明确而必然适用的 It is impossible to give hard-and-fast rules, but here are some points to consider. 给出明确的放之四海而皆准的准则是不可能的，但是下面几点可以考虑。

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.

ˌhard-and-ˈfast adjectiveChineseSyllable  

able to always definite, used Corpus and clear, be

hard-and-fast
ˌhard-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.