About the Usage of "When" Clauses as Adjective-clauses

Question

In the 19th century, Yukichi Fukuzawa, one of the greatest Japanese politicians and philosophers, wrote during his studying abroad:

"Language is a tool. It is like a hammer when you build a house."

The question is whether the usage of this "when" is correct (I mean, can the "when" act as "with which" or something like that?)

If yes, I'm glad if you show me some sample sentences using "when" of this usage.

If no, please let me know why it is wrong.

Oops! Note that I know these similar sample sequences: "I will never forget the time when we first met." "I can imagine his astonishment when she asked him to marry her." "This is a picture when I went to Paris."

Answer 1

Such when-clauses are often used to refer to the event, activity, or state in the abstract, as an exemplary situation, not as a specific instance that has actually taken place at a particular time.

When you're in love, the world seems brighter.

The mortgage is said to be "in default" when the borrower has failed to pay the debt service for an extended period.

It is not safe to go swimming when there is thunder and lightning.

Answer 2

Although I think that I do understand what he meant by that second sentence, it sounds a bit weird in English. Maybe it does so because it is elliptic?!

Probably he meant something like :

Language is a tool. It is like using a hammer when you build a house.

Now the meaning of when appears to become clearer. I think there is nothing particular about this use of when. The word is used in its basic temporal sense. Here 'when' refers not to a singular event in the past. It rather generalizes on a hypothetical situation: whenever you build a house.

It's the first part of that sentence and the sentence as a whole that I find rather strange. But may this be so because it's a literal translation from Japanese and that I am not familiar with Japanese metaphors?