Learn Swedish: Bygger barnen huset med verktygen själva? - Do the children build the house with the tools themselves?

In Swedish, just like in English, the preposition med (with) is used to indicate the tool or instrument used to perform an action. Here, the children are building med verktygen (with the tools).

What is the base form of verktygen, and why does it end in -en?

The base form is the ett-word ett verktyg (a tool). Because it ends in a consonant, the plural is exactly the same: verktyg (tools). To make it definite plural for "the tools", we add -en to get verktygen. This is a common pattern for ett-words that can sometimes trick learners into thinking it is a singular en-word.

Why is it själva instead of själv?

The word själv (oneself) works like an adjective and must agree with the noun it refers to. Since it refers back to barnen (the children), which is plural, it takes the plural ending -a to become själva (themselves).

Why is själva placed at the very end of the sentence?

In Swedish, when själv or själva is used to emphasize that someone did something independently or on their own, it typically goes at the end of the clause. Putting it right next to barnen would sound unnatural here.