هو يشد البرغي بمفتاح ربط.

Because the verb يشدّ already tells you the subject is he: third person, masculine, singular.

So the sentence could simply be:

يشدّ البرغي بمفتاح ربط.

Adding هو makes the subject explicit. In MSA, that can be done for:

• clarity
• emphasis
• contrast
• a textbook-style full sentence

So هو is not strictly necessary here, but it is perfectly correct.

يشدّ is in the imperfect form.

In MSA, the imperfect often covers both:

• he tightens
• he is tightening

The exact English translation depends on context. In a picture caption or simple description, either is possible.

So this verb does not force a distinction between simple present and present progressive the way English often does.

It is pronounced approximately ya-shuddu.

A few things matter here:

• يَ = ya
• شُ = shu
• دّ = a d sound that is doubled or held slightly longer

That doubled د is important because of the shadda.
So do not pronounce it like a single short d only. Think of it as:

yashud-du

The dictionary form is شَدَّ = shadda.

الـ is the definite article, so البرغي means the screw.

Arabic often uses the definite article in places where English also uses the, especially when talking about a specific object already understood from the situation.

In a sentence like this, the idea is usually:

• a particular screw
• the screw being worked on

So البرغي is natural here.

Because Arabic has no indefinite article.

English distinguishes:

• a wrench
• the wrench

Arabic usually does this by:

• leaving the noun without الـ for an indefinite meaning
• adding الـ for a definite meaning

So:

• مفتاح ربط = a wrench / wrench
• مفتاح الربط or المفتاح in another context could be definite, depending on structure and meaning

In this sentence, مفتاح ربط is indefinite, so it naturally corresponds to a wrench.

Here بـ means with, by means of, or using.

So:

• بمفتاح ربط = with a wrench / using a wrench

This بـ is a preposition, and like other Arabic prepositions, it makes the following noun genitive in fully vocalized Arabic.

That is why, in full vocalization, you would get something like:

بِمِفْتاحِ ...

It is two words:

• مفتاح = key; also used for certain tools, including wrench/spanner
• ربط = fastening, tying, connecting

Together, مفتاح ربط is a standard tool name meaning wrench or spanner.

Literally, it is something like a fastening tool/key, but you should understand it as the normal name of the tool, not as a word-for-word phrase every time.

Yes, it is basically an iḍāfa-type construction.

That means:

• the first noun is مفتاح
• the second noun is ربط
• together they function as one unit: wrench

In an iḍāfa:

• the first noun does not take الـ unless the whole phrase is definite
• the second noun determines definiteness

Here the phrase is indefinite, so it means a wrench.

In fully vocalized form, this would be:

مِفْتاحِ رَبْطٍ

after the preposition بـ.

Yes.

Arabic allows more than one natural word order. For example:

• هو يشدّ البرغي بمفتاح ربط.
• يشدّ البرغي بمفتاح ربط.

Both are correct.

The second version is very natural because the verb already contains the subject information.
The version with هو feels a bit more explicit.

So for a learner, it is useful to know:

• Arabic often drops subject pronouns when the verb already makes the subject clear
• adding the pronoun is still possible for emphasis or clarity

The dictionary form is:

شَدَّ

Its root is:

ش د د

This root has meanings connected with:

• pulling tight
• tightening
• making firm
• intensifying

So in this sentence, يشدّ means he tightens or he is tightening.

A careful fully vocalized version is:

هُوَ يَشُدُّ الْبُرْغِيَّ بِمِفْتَاحِ رَبْطٍ.

A few notes:

• هُوَ = subject pronoun
• يَشُدُّ = imperfect verb, third person masculine singular
• الْبُرْغِيَّ = direct object, so accusative
• بِمِفْتَاحِ = after بـ, so genitive
• رَبْطٍ = second term of the iḍāfa, also genitive

In normal unvocalized writing, those case endings are not shown, which is why the original sentence appears simply as:

هو يشد البرغي بمفتاح ربط.

Yes, a learner may notice that it does not look like a very basic native Arabic noun.

برغي is a technical word meaning screw, and it is commonly treated as a regular noun in modern usage. In fully inflected MSA, its ending can show case in ways that may look slightly less familiar to beginners.

But for practical reading, the important thing is simply:

• برغي = screw
• البرغي = the screw

So even if its morphology feels a little less transparent than a very basic noun, you can safely learn it as a standard vocabulary item.