Learn Dutch: Ik krijg de bout en de moer niet vast met de inbussleutel. - I cannot get the bolt and the nut tight with the Allen key.

In this lesson's structure, krijgen combined with a direct object and an adjective (like vast) expresses achieving a result through physical or mental effort. Saying ik krijg het vast implies managing to get it tight. If you used ik maak het vast, it simply means you are attaching it, without the nuance of trying hard to achieve the result.

Why is vast placed where it is, rather than at the very end of the sentence?

The adjective vast acts as the result of the action, so it sits at the end of the core clause, exactly where a separable prefix would go. The phrase met de inbussleutel is a prepositional phrase, and Dutch often places these at the very end of the sentence, after the core verbs or resultative adjectives.

Why does niet go exactly before vast?

In this sentence, niet is negating the resultative state itself. You are saying you get the bolt and nut niet vast (not tight). When negating the specific result in a krijgen + adjective construction, niet always goes immediately before that adjective.

Is inbussleutel spelled correctly? I usually hear native speakers pronounce it with an m.