Lijn de rail uit en maak hem vast.

Because uitlijnen is a separable verb.

In the dictionary, the verb is written as one word: uitlijnen. But in a normal main clause or command, the conjugated verb part comes earlier, and the particle uit moves to the end.

So:

• infinitive: uitlijnen
• command: Lijn de rail uit

This is a very common Dutch pattern:

• aandoen → Doe het licht aan
• opruimen → Ruim je kamer op
• vastmaken → Maak hem vast

So lijn ... uit is just the split form of uitlijnen.

Here, lijn is a verb form, not the noun lijn meaning line.

It is the imperative (command form) of uitlijnen:

• infinitive: uitlijnen
• stem / command form: lijn ... uit

Dutch imperatives usually use the verb stem, which is why you get:

• maak from maken
• lijn from uitlijnen

So in this sentence, both Lijn and maak are commands.

Because this is an imperative sentence: a command or instruction.

In Dutch, just like in English, the subject is usually left out in commands:

• English: Align the rail and fasten it.
• Dutch: Lijn de rail uit en maak hem vast.

The person being addressed is understood automatically. This is especially common in manuals, instructions, and step-by-step directions.

Because rail is a de-word in Dutch.

Dutch nouns take either:

• de
• het

You usually just have to learn which article belongs with each noun. For this word, the correct form is:

• de rail

That also affects how you refer back to it later with pronouns.

Here hem means it, not him.

In Dutch, pronouns often follow the grammatical gender of the noun, not natural gender. Since rail is a singular de-word, it can be referred to as hem in object position.

So:

• de rail → hem

If the noun were a het-word, you would usually expect het instead.

For a learner, the important point is:

• hem here refers back to de rail
• in English, you would translate it as it

Because vastmaken is also a separable verb, and object pronouns usually go between the conjugated verb and the separable particle.

So the order is:

• maak = conjugated verb
• hem = object pronoun
• vast = separable particle

That gives:

• Maak hem vast

This is the normal Dutch word order for separable verbs in main clauses:

• Doe het raam open
• Zet hem aan
• Maak hem vast

So hem comes before vast, not after it.

By itself, maken means to make or to do. But vastmaken is a fixed verb meaning to fasten, to attach, or to secure.

Literally, vast has the idea of fixed, firm, or not loose.

So:

• maken = to make
• vastmaken = to make fixed / to fasten / to secure

That means maak hem vast should be understood as one verbal idea: fasten it or secure it.

You would look them up in their full infinitive forms, not in the split command forms.

So:

• Lijn de rail uit → look up uitlijnen
• maak hem vast → look up vastmaken

This is important with separable verbs: in actual sentences they often split apart, but in dictionaries they are usually listed as one word.

Yes. It contains two coordinated imperatives joined by en:

1. Lijn de rail uit
2. maak hem vast

So the structure is:

• first do action 1
• then do action 2

This kind of instruction is very common in technical Dutch, where short direct commands are preferred.