Hi everyone, so i want to build and install a tow hitch on my car.

Im planning on replicating this
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With the square tubing for hitch instead of the J shaped one.

The doubt i got, is the 4 holes where you bolt the bar to the chasis.
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I see that my car has those, but i dont see any threads on them. What kind of hardware do you use to bolt them? do you need to put some kind of nutsert or something like that there?

Your help is appreciated.