Learn Hardcore German: In der Garage hat mein Vater eine Werkzeugkiste, in der alle Schraubenzieher und Zangen ordentlich liegen. - In the garage my father has a toolbox in which all screwdrivers and pliers lie neatly.

German main clauses must have the finite verb in second position (the V2 rule). The element in first position can be something other than the subject.

Neutral order: Mein Vater hat in der Garage eine Werkzeugkiste.
- 1st position: Mein Vater (subject)
- 2nd position: hat (verb)
With emphasis on the location: In der Garage hat mein Vater eine Werkzeugkiste.
- 1st position: In der Garage (adverbial phrase)
- 2nd position: hat (verb)
- The subject mein Vater moves behind the verb, but the meaning stays the same.
  This word order is very common and sounds natural, especially when you want to highlight where something is.

Why is it in der Garage and not in die Garage?

The preposition in can take dative (location) or accusative (direction):

Dative (Wo? – where?): static location
- in der Garage = in the garage (already there)
Accusative (Wohin? – where to?): movement into something
- in die Garage = into the garage (movement going there)

In this sentence, the toolbox is located in the garage, so it answers Wo? and uses the dative: in der Garage.

Why is it in der Garage and not im Garage?

Im is a contraction of in dem (preposition + masculine or neuter dative article).

im Keller = in dem Keller (Keller is masculine)
im Haus = in dem Haus (Haus is neuter)

But Garage is feminine: die Garage, dative der Garage.
You cannot contract in der in the same way, so it must be:

in der Garage, not im Garage.

Why is it eine Werkzeugkiste but later in der (relative pronoun), not in einer?

Two different things are happening here:

eine Werkzeugkiste
- eine is the indefinite article for a feminine noun in the nominative or accusative singular.
- Here it’s the direct object (accusative):
  - (Wer hat was?) → Mein Vater hat eine Werkzeugkiste.
in der in … eine Werkzeugkiste, in der …
- der here is not an article; it’s a relative pronoun meaning which / in which.
- It refers back to Werkzeugkiste (feminine, singular).
- The preposition in in a location phrase takes dative, so we need dative feminine singular: der.
- Therefore: in der = in which (referring to the toolbox).

So:

eine = article (accusative, feminine)
der = relative pronoun (dative, feminine, after in)

What exactly is the function of in der in …, in der alle Schraubenzieher und Zangen ordentlich liegen?

In der introduces a relative clause that gives extra information about Werkzeugkiste:

in der = in which (refers to the toolbox)
alle Schraubenzieher und Zangen = subject of the relative clause
ordentlich liegen = verb phrase (predicate)

Grammar-wise:

Werkzeugkiste: feminine, singular
Relative pronoun for feminine singular:
- Nominative: die
- Accusative: die
- Dative: der
Because of in (location), we need dative → der.

So in der = in + (dative feminine relative pronoun).

Why does the verb go to the end in …, in der alle Schraubenzieher und Zangen ordentlich liegen?

That is standard word order for subordinate clauses in German, including relative clauses.

Main clause: verb is in second position
- Mein Vater hat eine Werkzeugkiste.
Subordinate clause (introduced by a subordinating conjunction or relative pronoun): finite verb goes to the end
- … in der alle Schraubenzieher und Zangen ordentlich liegen.

So in this relative clause:

Introducer: in der (preposition + relative pronoun)
Middle part: alle Schraubenzieher und Zangen ordentlich
Verb at the end: liegen

Word order pattern: [in der] [subject + other stuff] [verb].

Why is liegen used instead of sind in the last part?

German often uses verbs of position rather than just sein (to be) to describe where objects are:

liegen – to lie (be lying, in a horizontal position)
stehen – to stand (be standing, vertical)
sitzen – to sit (be sitting)
hängen – to hang (be hanging)

In this sentence, tools in a toolbox are imagined as lying in it, so liegen is natural:

… in der alle Schraubenzieher und Zangen ordentlich liegen.
→ literally: in which all screwdrivers and pliers lie in an orderly way.

You could say … ordentlich sind, but it would sound less idiomatic and more generic; liegen paints a more precise picture of how they are stored.

Are Schraubenzieher and Schraubenzieher (plural) the same form? How do I know it’s plural?

Yes, Schraubenzieher has the same form in singular and plural:

Singular: der Schraubenzieher – ein Schraubenzieher
Plural: die Schraubenzieher

You know it’s plural here because of:

the determiner: alle Schraubenzieher (alle = all → plural)
the coordination: alle Schraubenzieher und Zangen (list of tools, understood as plural)

In general, for nouns with identical singular and plural forms, you must rely on articles, determiners, or context to see the number.

Why is Zangen in the plural? Can I say eine Zange?

The noun Zange (pliers) works a bit like scissors in English:

There is a singular: die Zange, eine Zange
(e.g. eine Zange kaufen = to buy a pair of pliers)
But very often you talk about them in the plural, especially in sets of tools:
- Zangen = different kinds of pliers (combination pliers, needle-nose pliers, etc.)

In alle Schraubenzieher und Zangen the speaker is probably thinking of several kinds of pliers, which is why the plural is used. Saying alle Schraubenzieher und Zange would be ungrammatical; it must be Zangen to match alle.

What is ordentlich doing here? Is it an adjective or an adverb, and why doesn’t it change ending?

In this sentence, ordentlich is an adverb describing how the tools liegen (lie):

Sie liegen ordentlich. = They lie neatly / in an orderly way.

As an adjective before a noun, ordentlich would take endings:

eine ordentliche Werkzeugkiste – a neat toolbox
ordentliche Zangen – neat pliers

As an adverb, German adjectives normally have no ending:

Er arbeitet ordentlich. – He works neatly.
Die Schraubenzieher liegen ordentlich. – The screwdrivers lie neatly.

So here it stays in its base form because it’s modifying the verb, not a noun.

Why is there a comma before in der? Could we leave it out?

The comma is required because in der alle Schraubenzieher und Zangen ordentlich liegen is a relative clause.

Rule: All relative clauses in German are set off by commas.

Mein Vater hat eine Werkzeugkiste, in der alle Schraubenzieher und Zangen ordentlich liegen.

You cannot omit this comma in standard German; leaving it out would be considered incorrect in formal writing.

Could I say …, wo alle Schraubenzieher und Zangen ordentlich liegen instead of …, in der … liegen?

Yes, you can say:

Mein Vater hat eine Werkzeugkiste, wo alle Schraubenzieher und Zangen ordentlich liegen.

However:

Using wo like this is quite common in spoken and colloquial German.
In standard written German, especially in formal contexts, preposition + relative pronoun (in der) is preferred and often considered more correct or more elegant.

So:

More formal/standard: … eine Werkzeugkiste, in der alle Schraubenzieher und Zangen ordentlich liegen.
More colloquial: … eine Werkzeugkiste, wo alle Schraubenzieher und Zangen ordentlich liegen.