There are no hard-and-fast rules you need to follow when considering 40th birthday cake designs, but it is a good idea to keep the birthday person's tastes and preferences in mind.
There are no hard-and-fast rules about wearing goth makeup.
In fact, as mentioned in the article Mouse, there is no possibility of defining the term "rat" when used in a sense other than as relating to the two species above mentioned; while there is also no hard-and-fast limit between the terms "rats" and "mice" when these are likewise employed in their now extended sense, "rats" being merely larger "mice," and vice versa.
The ecclesiastical polity of the Church is Wesleyan and its theology is Arminian: there is no hard-and-fast rule about baptism.
Instead of requiring from its population all kinds of work and reducing its ordinary occupations to a hard-and-fast routine meeting in a slow and unskilled manner all possible contingencies, the local group began to move, to call in workmen from abroad for tasks of a special nature, and to send its own workmen to look out for profitable employment in other places.
- In the one case the stimulus induces indefinite variation, in the other definite; but no hard-and-fast line can be drawn between them.