Ons toets nie soseer draaiknoppe nie, maar sluitmeganismes.

It is a contrast pattern meaning not so much ... but rather ... or not really ... but rather ....

So here:

• nie soseer draaiknoppe nie = not so much knobs
• maar sluitmeganismes = but rather locking mechanisms

This is a very common Afrikaans way to correct or refine what is being focused on.

Afrikaans usually uses double negation.

In a basic negative sentence, you often get:

• first nie near the part being negated
• second nie later in the clause

Here the structure is built into the expression:

• Ons toets nie soseer draaiknoppe nie, maar sluitmeganismes.

So the two nie words are not two separate English-style negatives. They are just normal Afrikaans negation.

Soseer means something like so much, to such an extent, or particularly.

You will often see it in the fixed expression:

• nie soseer X nie, maar Y

That whole pattern is more important than the word soseer on its own. For a learner, it is often best to remember the full phrase as one unit.

Yes, ons means we.

In some contexts, ons can also mean us, because Afrikaans does not distinguish between we and us the way English does.

Examples:

• Ons toets ... = We test ...
• Hy sien ons. = He sees us.

In this sentence, ons is clearly the subject, so it means we.

Because Afrikaans verbs usually do not change form for different subjects in the present tense.

So you get:

• ek toets
• jy toets
• ons toets
• hulle toets

That is much simpler than English, where you have forms like I test but he tests.

Here:

• toets = test / are testing

Draaiknoppe is a compound noun.

It is built from:

• draai = turn
• knop = knob
• knoppe = knobs

So draaiknoppe literally suggests turn-knobs, which in natural English would usually be knobs, rotary knobs, or control knobs, depending on context.

A useful thing to know about Afrikaans is that compound nouns are extremely common.

It is also a compound noun:

• sluit = close / lock
• meganismes = mechanisms

So sluitmeganismes means locking mechanisms or sometimes closing mechanisms, depending on context.

In many technical or mechanical contexts, locking mechanisms is the most natural translation.

Because the sentence is talking about categories or types of things in general, not one specific item.

So:

• draaiknoppe = knobs
• sluitmeganismes = locking mechanisms

This is normal in both Afrikaans and English when speaking generally.

Because the sentence is speaking about things in general, not specific known objects.

Compare:

• Ons toets draaiknoppe. = We test knobs.
• Ons toets die draaiknoppe. = We test the knobs.

Adding die would make the nouns more specific. Without die, the statement sounds more general or categorical.

Here maar means but or more naturally but rather.

So the sentence sets up a contrast:

• not X
• but Y

That is why maar works very naturally after nie soseer ... nie.

Not especially. The sentence follows a normal main-clause pattern:

• Ons = subject
• toets = verb
• nie soseer draaiknoppe nie = negated/contrasted object phrase
• maar sluitmeganismes = contrasting phrase

So the core structure is straightforward. The main thing that may look unusual to an English speaker is the Afrikaans double negation and the fixed contrast pattern nie soseer ... nie, maar ....

Not exactly.

If you remove the nuance, that is close, but nie soseer ... nie, maar ... is softer and more nuanced than a simple correction.

It means something like:

• It is not so much knobs that we are testing, but rather locking mechanisms.
• Our focus is less on knobs and more on locking mechanisms.

So it does not necessarily mean knobs are completely excluded. It often means the real emphasis is on the second item.

A more direct version would be:

• Ons toets nie draaiknoppe nie, maar sluitmeganismes.

That means:

• We are not testing knobs, but locking mechanisms.

Compared with that, nie soseer draaiknoppe nie, maar sluitmeganismes sounds more like not so much knobs as locking mechanisms. It is less absolute and more contrastive.