Knappvrideren låser reilen.

Because Norwegian usually writes compound nouns as a single word.

Here, knappvrideren is built like this:

• knapp
• vrider
• -en

So instead of writing something like knapp vrider, Norwegian combines the parts into one compound noun. This is very common in Norwegian, much more than in English.

The ending -en is the definite singular ending, so it means the.

Compare:

• en knappvrider = a thumbturn / a knob turner
• knappvrideren = the thumbturn / the knob turner

In English, the comes before the noun. In Norwegian, it is often attached to the end of the noun.

For the same reason: reilen already includes the meaning the bolt / the deadbolt.

Compare:

• en reile = a bolt / a deadbolt
• reilen = the bolt / the deadbolt

So this sentence has two definite nouns:

• knappvrideren = the thumbturn
• reilen = the bolt

Norwegian often marks definiteness with an ending instead of a separate word.

The dictionary forms are:

• knappvrideren → knappvrider
• låser → å låse
• reilen → reile

So if you looked them up, you would normally search for knappvrider, låse, and reile.

Here it is definitely a verb: locks.

But yes, låser can also be a noun form in other contexts, because it can be the plural of lås = lock.

In this sentence, though, the structure makes it clear that låser is a verb:

• Knappvrideren = subject
• låser = verb
• reilen = object

So the pattern is the normal subject + verb + object order.

Låser is present tense.

The verb is:

• infinitive: å låse = to lock
• present: låser = locks / is locking
• past: låste = locked
• past participle: låst = locked

In a sentence like this, låser is often best understood as a general present, especially in technical descriptions: The thumbturn locks the bolt.

Reile is a technical lock term. In English, it is often translated as bolt, and in many contexts more specifically deadbolt.

The exact English word can depend on the type of lock, so you may see different translations in manuals or product descriptions. The important point is that it refers to the locking bolt inside the mechanism.

It is understandable, but it sounds fairly technical or hardware-specific.

You are especially likely to see it in:

• manuals
• product descriptions
• locksmith or door-hardware contexts

In natural English, the most idiomatic equivalent is often thumbturn rather than a very literal translation.

Because this is the normal word order for a simple main clause in Norwegian:

• Knappvrideren = subject
• låser = finite verb
• reilen = object

So it follows the basic pattern subject + verb + object, just like English in a simple sentence.

It is also a good example of Norwegian’s main-clause rule that the finite verb comes early in the sentence, typically in second position.

You can do a literal translation, but it may sound awkward.

A very literal version would be something like:

• The knob-turner locks the bolt

A more natural English translation in a lock-related context would usually be:

• The thumbturn locks the bolt
• The thumbturn locks the deadbolt

So with Norwegian compounds, it is often better to translate the function of the word, not just each part separately.