En la ferretería del barrio, la dependienta me explicó qué tornillos eran mejores para el estante.

Because de + el contracts to del in Spanish.

• de el barrio → del barrio
• This is mandatory with el
• The only common exception is when el is part of a proper name, such as de El Escorial

So la ferretería del barrio means the neighborhood hardware store or more literally the hardware store of the neighborhood.

Ferretería means hardware store.

It is a very common word in Spain for a shop that sells things like:

• screws
• nails
• tools
• locks
• brackets
• household repair items

So this is a normal, everyday Spain Spanish word.

La dependienta means the female shop assistant / sales assistant.

A few useful points:

• dependiente = male shop assistant
• dependienta = female shop assistant

In Spain, this word is normal and common in shops. In other Spanish-speaking regions, people may prefer other words, such as:

• empleada
• vendedora
• señora de la tienda, depending on context

Here, la dependienta clearly tells you the person helping the speaker is a woman.

The comma separates the opening location phrase from the main part of the sentence.

• En la ferretería del barrio, = At/In the neighborhood hardware store,
• la dependienta me explicó... = the main action

This is similar to English when you begin with a setting or location:

• At the hardware store, the assistant explained...

The comma helps readability, but in short sentences Spanish punctuation can sometimes be a little flexible. Here it is very natural.

Because me means to me.

• explicó = she explained
• me explicó = she explained to me

Spanish often uses an indirect object pronoun where English may or may not express it directly.

So:

• La dependienta explicó... = The assistant explained...
• La dependienta me explicó... = The assistant explained to me...

Explicó is the preterite of explicar, used for a completed action in the past.

• explicó = she explained
• This presents the explanation as a finished event

That fits the sentence well: the shop assistant explained something at that moment or during that interaction.

Compare:

• me explicó = she explained to me, completed event
• me explicaba = she was explaining to me / used to explain to me

Here, the preterite is the natural choice because it describes a specific completed action.

Because qué is normally used before a noun, while cuáles usually stands alone.

So:

• qué tornillos = which screws
• cuáles eran mejores = which ones were better

In standard Spanish:

• qué + noun → qué tornillos
• cuál/cuáles without a noun → cuáles eran mejores

That is why the sentence says:

• me explicó qué tornillos eran mejores

not usually:

• me explicó cuáles tornillos eran mejores

Some varieties may allow cuáles before a noun in certain contexts, but for learners, qué + noun is the safest and most standard choice.

Because it is an interrogative/exclamative word used in an indirect question.

Even though this is not a direct question with question marks, it still contains an indirect question:

• qué tornillos eran mejores = which screws were better

Spanish gives an accent to question words in both direct and indirect questions:

• ¿Qué tornillos eran mejores?
• Me explicó qué tornillos eran mejores.

So the accent is correct and important.

Because eran works better here to describe which screws were the better option in that situation.

In this sentence, the speaker is reporting the content of the explanation: the assistant explained which screws were better for the shelf. The imperfect eran is natural because it describes a state or characteristic rather than a single finished event.

• eran mejores = were better / were the better choice
• fueron mejores would sound more like turned out to be better in a completed event sequence

So eran mejores is the normal choice when talking about suitability or qualities being explained.

Because it agrees with tornillos, which is plural.

• el tornillo = the screw
• los tornillos = the screws
• mejor = better
• mejores = better, plural

So:

• qué tornillos eran mejores

means which screws were better

If the noun were singular, you would get:

• qué tornillo era mejor

Because para expresses purpose, intended use, or suitability.

Here the meaning is:

• the screws were better for the shelf
• the screws were more suitable for attaching or supporting the shelf

That is exactly the kind of idea para expresses.

By contrast, por usually relates to things like:

• cause
• movement through
• exchange
• means
• duration

So para el estante is the correct choice here.

Usually estante means shelf.

Depending on context, it can refer to:

• a single shelf
• sometimes shelving or a shelf unit, depending on the speaker and region

In this sentence, the most natural reading is shelf:

• the assistant explained which screws were better for the shelf

If you wanted to be more explicitly bookcase / shelving unit, other words might appear depending on region, such as:

• estantería
• librería in some contexts, though that can also mean bookshop, so it can be ambiguous

Yes, Spanish word order is flexible, but this version is the most neutral and natural.

The basic structure is:

• la dependienta = subject
• me explicó = verb + indirect object
• qué tornillos eran mejores para el estante = what she explained

You could rearrange parts for emphasis, but the original is the clearest standard order.

For example:

• En la ferretería del barrio, me explicó la dependienta qué tornillos eran mejores...

This is possible, but it sounds more marked or literary. For everyday Spanish, the original sentence is better.

It often suggests the local neighborhood hardware store, the one associated with that area.

So depending on context, it can feel like:

• the hardware store in the neighborhood
• the local hardware store
• the neighborhood hardware store

Spanish often uses this structure to identify a familiar place:

• el bar del barrio
• la panadería del barrio
• la farmacia del barrio

It gives the sentence a natural, everyday, local feel.