unjeonhal ttaeneun myeonheojeungeul jigabe kkok neoheo dwo.

운전할 때 means when driving or while driving.

Breaking it down:

• 운전하다 = to drive
• 운전할 = the form that modifies a following noun
• 때 = time / moment / when
• 는 = topic marker

So 운전할 때는 is literally something like as for when you drive.

The 는 adds a topic or contrast nuance. It can sound like:

• when driving, at least...
• as for when you drive...

In natural English, we usually just translate it as when you drive or when driving.

Korean often uses the future/attributive form -(으)ㄹ before 때 to refer to a general occasion or situation:

• 운전할 때 = when driving / when you drive

This is the most natural and common form here.

운전하는 때 is grammatically possible in some contexts, but it sounds less natural for this everyday meaning. Native speakers usually say 운전할 때.

A useful pattern to remember:

• V-(으)ㄹ 때 = when doing V / when one does V

Examples:

• 집에 갈 때 = when going home
• 잘 때 = when sleeping
• 운동할 때 = when exercising

면허증 means license, and here it specifically means a driver’s license because the sentence is about driving.

• 면허증 = license/certificate
• 을 = object marker

So 면허증을 marks driver’s license as the thing being put somewhere.

The action is 넣다 = to put in, so the object marker makes sense:

• 면허증을 넣다 = to put the license in

Because 지갑 is the place/destination where the license is being put.

• 지갑에 = in/into the wallet
• 에 marks location or destination

So:

• 면허증을 = the thing being put
• 지갑에 = the place it goes

Compare:

• 책을 가방에 넣다 = put the book in the bag
• 열쇠를 주머니에 넣다 = put the key in your pocket

If you said 지갑을, that would make wallet the object, which is not what this sentence is doing.

꼭 means definitely, for sure, be sure to, or without fail.

In this sentence, it adds emphasis and makes the instruction stronger:

• 꼭 넣어 둬 = make sure you keep it in there
• don’t forget to put it in your wallet

It often appears in advice, reminders, or strong recommendations:

• 꼭 오세요. = Please definitely come.
• 약 꼭 먹어. = Be sure to take your medicine.
• 문 꼭 닫아. = Make sure you close the door.

This is a very important nuance.

• 넣어 = put it in
• 넣어 둬 = put it in and leave it there / keep it in there in advance

The grammar here is -아/어 두다, which means doing something beforehand or leaving something in a certain state for later convenience.

So:

• 면허증을 지갑에 넣어 = put your license in your wallet
• 면허증을 지갑에 넣어 둬 = put your license in your wallet and keep it there, so it’s ready when needed

That fits the context very well, because a driver’s license is something you should have ready when driving.

둬 is a contracted spoken form.

The full underlying expression is:

• 넣어 두다

In casual speech, 두어 often contracts to 둬:

• 넣어 두어 → 넣어 둬

So:

• 넣어 둬 = casual spoken form
• 넣어 두어 = less common in everyday conversation
• 넣어 두다 = dictionary/plain form

This contraction is very common and natural in speech.

It is casual / informal speech.

The ending -둬 is used when speaking casually to:

• a friend
• someone younger
• a child
• someone you are close to

If you wanted to say it politely, you could say:

• 운전할 때는 면허증을 지갑에 꼭 넣어 두세요.

That means the same thing, but in a polite style.

Yes, the subject is omitted, and it is understood as you.

Korean often leaves out subjects when they are obvious from context. In this kind of advice or instruction sentence, the implied subject is usually:

• you

So the full sense is:

• When you drive, make sure you keep your license in your wallet.

Korean does this very naturally, and learners should get used to subjects being omitted.

Good question. The full word for driver’s license is often 운전면허증.

But in context, 면허증 alone is commonly understood to mean the driver’s license, especially when the topic is driving.

So both can work:

• 운전면허증을 지갑에 꼭 넣어 둬.
• 면허증을 지갑에 꼭 넣어 둬.

The shorter 면허증 sounds natural because the context already makes the meaning clear.

Yes, depending on the context, that is actually a very natural English translation.

Literally, the Korean says:

• put your license in your wallet and keep it there

But in smoother English, we often say:

• Make sure you carry your license in your wallet when you drive.

That captures the real intention better.

So the Korean is about both:

1. the action of putting it there, and
2. the resulting state of having it there when needed

Yes. In casual speech, 때는 is often contracted to 땐.

So:

• 운전할 때는 면허증을 지갑에 꼭 넣어 둬.
• 운전할 땐 면허증을 지갑에 꼭 넣어 둬.

These mean the same thing.

The 땐 form is very common in conversation and informal writing.

Yes. It is normally written as 넣어 둬, with a space.

That is because it comes from the auxiliary construction:

• 넣어 두다

So standard spacing is:

• 넣어 둬
• 넣어 두세요
• 넣어 두다

In casual writing, some people may write it together, but the standard form is spaced.

Yes, but the nuance is a little different.

For example:

• 운전할 때는 면허증을 꼭 가지고 다녀.

This means:

• When you drive, make sure you carry your license with you.

That focuses on having it with you.

By contrast:

• 면허증을 지갑에 꼭 넣어 둬.

focuses more specifically on:

• putting it in your wallet
• keeping it there in advance

So both are natural, but the original sentence is more specific about where to keep it.