Senhor, sem a chave de fendas, não consigo apertar a dobradiça da porta.

Senhor means sir. It is being used as a form of address, directly to the person being spoken to.

The comma is there because Senhor is a vocative: a word used to call or address someone. Portuguese punctuates this like English:

• Senhor, sem a chave de fendas...
• Sir, without the screwdriver...

Without the comma, it would be less clear that the speaker is addressing someone.

Both are possible, but they feel slightly different.

• sem a chave de fendas = without the screwdriver
  This usually suggests a specific screwdriver, known or understood in the situation.
• sem chave de fendas = without a screwdriver / without any screwdriver
  This is more general.

In this sentence, sem a chave de fendas sounds natural because the speaker probably means a particular tool that is needed for the job.

Because Portuguese has some contractions, but not all combinations contract.

• de + a = da
• de + o = do
• em + a = na
• em + o = no

So de a porta becomes da porta.

But sem + a does not normally contract in standard Portuguese, so it stays sem a.

Chave de fendas is the standard European Portuguese word for a screwdriver, especially the traditional flat-head kind.

Literally, it is something like slot tool/key, because fenda means slot or groove.

In real use, learners should simply remember:

• chave de fendas = screwdriver

Here, consigo is the 1st person singular present of the verb conseguir:

• eu consigo = I can / I manage
• eu não consigo = I can’t / I’m not able to

So in this sentence:

• não consigo apertar = I can’t manage to tighten

This is different from the other Portuguese word consigo used as a pronoun in some contexts. In this sentence, it is clearly the verb form from conseguir.

This is a very common learner question, because both can translate as I can’t.

• não consigo = I’m not able / I can’t manage
• não posso = I’m not allowed / I can’t / I may not

In this sentence, the problem is practical: the speaker lacks the right tool. So não consigo is the better choice.

It means something like:

• Without the screwdriver, I can’t manage to tighten the hinge.

If you said não posso, it might sound more like permission or general possibility, not specifically inability caused by the situation.

Because conseguir is followed by another verb in the infinitive.

This is a very common structure in Portuguese:

• consigo fazer = I can manage to do
• não consigo abrir = I can’t open
• não consigo apertar = I can’t tighten

So:

• não consigo apertar a dobradiça
  literally: I do not manage to tighten the hinge

Yes. Apertar has several meanings depending on context. Common ones include:

• to squeeze
• to press
• to tighten

In this sentence, because we are talking about a hinge and a screwdriver, apertar means to tighten.

That is very normal in Portuguese. The exact English translation depends on what is being tightened, pressed, or squeezed.

Dobradiça means hinge.

It is a feminine noun, so it takes feminine forms:

• a dobradiça
• a dobradiça da porta

The ending -a often signals a feminine noun, though not always. In this case, you simply learn it as:

• a dobradiça = the hinge

Portuguese usually expresses this idea with a structure like noun + de + noun:

• a dobradiça da porta = the hinge of the door = the door hinge

English often uses a noun directly before another noun, but Portuguese usually does not do that in the same way.

Also notice the articles:

• a dobradiça
• a porta
• da = de + a

So the full phrase literally means:

• the hinge of the door

Portuguese normally makes a sentence negative by putting não before the verb:

• consigo = I can / I manage
• não consigo = I can’t / I don’t manage

So the pattern is very straightforward:

• não + verb

Examples:

• não sei = I don’t know
• não tenho = I don’t have
• não consigo = I can’t manage

Yes, it is understandable and natural enough in European Portuguese.

A native speaker might also say something slightly more specific, depending on what exactly needs tightening, for example:

• Senhor, sem a chave de fendas, não consigo apertar a dobradiça da porta.
• Senhor, sem a chave de fendas, não consigo apertar os parafusos da dobradiça da porta.

The second version is a bit more precise, because in practice you usually tighten the screws of the hinge rather than the hinge itself. But the original sentence is still perfectly reasonable.

The ç is called c cedilhado. It makes the c sound like s before a, o, or u.

So in dobradiça, the ç is pronounced like s.

That means:

• dobradiça sounds roughly like do-bra-DEE-sa in an English-friendly approximation, though the real European Portuguese pronunciation is of course different.

A useful spelling rule is:

• before e or i, plain c can already sound like s
• before a, o, or u, Portuguese uses ç when it wants that s sound

So dobradiça is spelled with ç to keep the s sound before a.