Al final, hubo que apretar la tuerca con el alicate antes de volver a colocar el colchón.

Al final means in the end, eventually, or after everything else. It is often used to show the final outcome of a situation.

In this sentence, it tells you that after whatever happened before, the last thing that was necessary was tightening the nut before putting the mattress back.

A few nuances:

• Al final = in the end / eventually
• Finalmente = finally, often a bit more formal
• In everyday Spanish, al final is extremely common

The comma after it is natural because it works like an introductory phrase.

Hubo que + infinitive means it was necessary to... or we had to... / someone had to..., without saying exactly who.

So:

• hubo que apretar = it was necessary to tighten
• more naturally in English: we had to tighten or the nut had to be tightened, depending on context

This is an impersonal structure:

• hay que = one must / you have to / it is necessary to
• había que = it was necessary to / one had to in a more ongoing or background sense
• hubo que = it became necessary to / it was necessary to for a specific completed situation

Because hubo que and tuvo que do different things.

• hubo que + infinitive is impersonal: it does not name who had to do it
• tuvo que + infinitive means he/she/it had to..., so it needs a specific subject

Compare:

• Hubo que apretar la tuerca. = It was necessary to tighten the nut.
• Juan tuvo que apretar la tuerca. = Juan had to tighten the nut.

So the original sentence keeps the focus on the action and necessity, not on the person doing it.

This is a very common learner question.

• hubo que usually refers to a specific completed necessity in the story
• había que often sounds more like background information, a general obligation, or something ongoing

Here, the sentence describes a specific moment in a sequence of actions:

1. tighten the nut
2. then put the mattress back

So hubo que fits well because it presents that need as a completed event in the narrative.

Compare:

• Hubo que apretar la tuerca... = at that moment, this had to be done
• Había que apretar la tuerca... = it was necessary to tighten the nut, more as a general situation or ongoing requirement

Because after haber que you use an infinitive.

Structure:

• haber que + infinitive

Examples:

• Hay que estudiar.
• Había que esperar.
• Hubo que salir.

So:

• hubo que apretar is grammatically the normal pattern

Also, apretar here means to tighten, not just to squeeze. Spanish often uses apretar for making something tighter:

• apretar un tornillo
• apretar una tuerca

Because la tuerca refers to a specific nut that is already understood in the situation.

Spanish often uses the definite article when the object is identifiable from context. In a repair or assembly context, there is probably one particular nut they are talking about.

So:

• la tuerca = the nut
• una tuerca = a nut / some nut, not yet identified

This is very natural in Spanish when the speaker assumes the listener knows which object is meant.

Yes, alicate can be singular, and here el alicate means the pliers / the tool.

Learners often expect a plural form because in English pliers is plural. Spanish can do both depending on usage:

• el alicate
• los alicates

In many contexts, especially in everyday speech, people may say los alicates for one tool. But the singular el alicate is also correct.

As for con el alicate:

• con = with
• el alicate = the pliers / the tool

The definite article el suggests a specific tool, probably the one available or already mentioned.

Yes, very possibly.

Both can be found, depending on the speaker and region:

• con el alicate
• con los alicates

The sentence you were given simply uses the singular form. A learner should mainly understand that this word refers to a hand tool used for gripping or tightening.

So the important point is not that one is always right and the other always wrong, but that Spanish may treat this tool as:

• a singular object: el alicate
• or in a plural form: los alicates

Because after antes de, Spanish normally uses an infinitive when no new subject is introduced.

So:

• antes de + infinitive

Examples:

• antes de salir
• antes de comer
• antes de volver a colocar el colchón

This is the equivalent of English:

• before leaving
• before eating
• before putting the mattress back

If Spanish wanted to introduce a different subject and a full clause, it would use a different structure, often with antes de que:

• antes de que volviéramos a colocar el colchón

But in your sentence, the infinitive is the natural choice.

Volver a + infinitive means to do something again.

So:

• volver a colocar = to place again / to put back

Here it clearly means put the mattress back into place.

Breakdown:

• volver a = to do again / back
• colocar = to place / position / put

This is a very common structure in Spanish:

• volver a intentar = try again
• volver a empezar = start again
• volver a poner = put back / put again

Both are possible, but colocar often suggests placing something in its proper position a bit more carefully or precisely.

So:

• poner el colchón = put the mattress
• colocar el colchón = place the mattress / position the mattress

In many real situations, the difference is small. But colocar can sound slightly more deliberate or practical, which fits a sentence about moving and refitting something.

Yes. Spanish word order is fairly flexible, especially with adverbial phrases like al final and antes de....

For example, these are possible:

• Hubo que apretar la tuerca con el alicate al final, antes de volver a colocar el colchón.
• Antes de volver a colocar el colchón, hubo que apretar la tuerca con el alicate.

The original version is natural because it presents the sequence clearly:

1. Al final = final stage of the situation
2. hubo que apretar la tuerca = necessary action
3. antes de volver a colocar el colchón = when it had to happen

So the original order is good, but not the only grammatical one.

No. Apretar has a broader meaning: to press, to squeeze, to tighten, depending on context.

Examples:

• apretar un botón = press a button
• apretar la mano = squeeze someone’s hand
• apretar una tuerca = tighten a nut

So in this sentence, the object la tuerca tells you that apretar should be understood as tighten.