Guarda el alicate en el cajón, por si la tuerca vuelve a estar suelta.

Yes. Guarda is the tú imperative of guardar.

So Guarda el alicate... means Put/keep the pliers away... or Store the pliers...

For tú commands in regular verbs:

• -ar verbs use the él/ella/usted present form
• guardar → guarda

Examples:

• Habla = Speak
• Mira = Look
• Guarda = Put away / keep

If you were speaking more formally, you would say:

• Guarde el alicate... for usted

This is a very common point of confusion.

In Spanish, alicate can be treated as a singular noun, even though the object has two arms and English uses the plural pliers.

So:

• el alicate = the pliers
• un alicate = a pair of pliers / a set of pliers

In some contexts, you may also hear alicates, especially when referring to different kinds of pliers or tools in general. But in this sentence, el alicate is perfectly natural.

So the grammar follows Spanish, not English:

• Guarda el alicate... not
• Guarda los alicates... unless you specifically mean more than one tool or a plural usage.

Spanish uses definite articles more often than English.

Here, el alicate, el cajón, and la tuerca refer to specific things that both speaker and listener can identify:

• the pliers
• the drawer
• the nut

Even when English might say something like Put pliers in a drawer, Spanish often prefers the article if the item is known or understood from context.

So:

• Guarda el alicate en el cajón sounds natural as Put the pliers in the drawer

Because en expresses location inside something: in the drawer.

• en el cajón = in the drawer

If you say al, that usually means to the and often suggests movement toward a place, not being placed inside it in this way.

With containers, drawers, boxes, etc., Spanish normally uses:

• meter/poner/guardar algo en...
• Put/store something in...

Examples:

• Pon las llaves en el cajón.
• Guarda los papeles en la carpeta.

So en el cajón is the natural choice.

Por si means in case.

It introduces a possible future situation that explains why you should do something now.

So:

• Guarda el alicate en el cajón, por si... = Put the pliers in the drawer, in case...

The important thing to remember is that por si is followed by the indicative, not the subjunctive.

Here:

• por si la tuerca vuelve a estar suelta

That is normal Spanish.

Because after por si, Spanish normally uses the indicative.

This is different from some other expressions of possibility or purpose that often trigger the subjunctive.

So:

• por si vuelve not
• por si vuelva

Why? Because por si presents something as a possible circumstance: in case it happens.

More examples:

• Llévate un paraguas por si llueve.
• Te doy mi número por si necesitas ayuda.

Both use the indicative:

• llueve
• necesitas

Volver a + infinitive means to do something again or to become something again, depending on the verb.

Here:

• volver a estar = to be again
• la tuerca vuelve a estar suelta = the nut becomes loose again / is loose again

This structure is extremely common:

• volver a + infinitive

Examples:

• Volvió a llamar. = He/She called again.
• Voy a verlo otra vez. = I’m going to see him again.
• La puerta vuelve a estar abierta. = The door is open again.

Yes, often you could express a similar idea with otra vez, but volver a + infinitive is very common and often sounds more natural.

Compare:

• La tuerca vuelve a estar suelta.
• La tuerca está suelta otra vez.

Both can mean The nut is loose again.

A slight difference:

• vuelve a estar emphasizes the repetition of the state/change
• está suelta otra vez simply states that the situation is true again

In many everyday contexts, both work.

Because suelta here describes a temporary condition or state, not an essential characteristic.

• estar suelta = to be loose
• ser would sound wrong here

The nut is not inherently a loose nut by nature; it is in a loose condition right now or again.

This is a classic ser vs estar case:

• estar for condition/state
• ser for identity, essential characteristics, classification, etc.

Examples:

• La puerta está abierta.
• El tornillo está flojo.
• La tuerca está suelta.

Because it agrees with la tuerca, which is a feminine singular noun.

• la tuerca = feminine singular
• adjective must match → suelta

Compare:

• el tornillo está suelto
• la tuerca está suelta
• los tornillos están sueltos
• las tuercas están sueltas

This is normal adjective agreement in Spanish.

Yes, here tuerca means the hardware nut used with bolts and screws, not an edible nut.

Spanish often uses the same type of everyday word distinction through context:

• tuerca = mechanical nut
• nuez = walnut
• fruto seco or specific names for edible nuts in general contexts

Because the sentence includes alicate and the idea of something being suelta, the mechanical meaning is clear.

From a real-world tools perspective, yes, a wrench or spanner might often be more appropriate. But linguistically, the sentence is still fine.

Language-learning examples are often built to illustrate vocabulary and grammar, not perfect tool choice. The sentence is mainly useful for showing:

• the imperative guarda
• the expression por si
• volver a + infinitive
• estar suelta

So even if a native speaker might sometimes choose a different tool word in real life, the Spanish itself is natural.

Yes. Guardar has a wider range than the English verb guard might suggest.

Common meanings include:

• to put away
• to store
• to keep
• to save

In this sentence, guarda el alicate en el cajón means something like:

• Put the pliers away in the drawer
• Keep/store the pliers in the drawer

So don’t connect guardar too closely only with English guard.

It is very natural here because por si la tuerca vuelve a estar suelta adds the reason or precaution after the main command.

So the structure is:

• main instruction: Guarda el alicate en el cajón
• added explanation: por si la tuerca vuelve a estar suelta

The comma helps separate those parts and makes the sentence easier to read. In short everyday writing, punctuation can vary a bit, but the comma is completely normal here.

Yes. Some natural alternatives are:

• Guarda el alicate en el cajón por si la tuerca se afloja otra vez.
• Deja el alicate en el cajón, por si la tuerca vuelve a estar floja.
• Ten el alicate a mano por si la tuerca vuelve a soltarse.

These are slightly different in nuance:

• guardar = put away/store
• dejar = leave
• tener a mano = keep handy
• aflojarse / soltarse = become loose

But the original sentence is grammatically correct and natural.