There are many expressions commonly used in English with the comparison form ‘as … as’.
There is no magic rule to help you remember them. You just have to learn them. Sorry!
Take a look at the examples below.
As plain as day.
If something is as plain as day it is very obvious or very noticeable.
E.g. After the disastrous presentation and terrible feedback it was as plain as day that we would not win the contract.
As busy as a bee.
If someone is as busy as a bee they are extremely busy or very active.
E.g. He never stops. He’s as busy as a bee the whole day. It’s no surprise he’s so tired in the evenings.
As dead as a doornail.
If someone or something is as dead as a doornail they are undoubtedly dead. It can also be used to describe an idea, a project or a proposal that now has no chance of being realised and is totally defunct.
E.g. Forget it. Your idea from yesterday’s meeting is as dead as a doornail. The CEO will not approve extra funding for the project.
Have fun learning English!
Louise