Could you give me a source for this?

Preferably a Finnish one. Not by language (although am Finnish so not an issue) but like a reliable source in Finland documenting that’s what they’re for?

I know we do have lots of infra designed “in case of Russian attack”, mainly the direction of roads on the eastern border, but I’d like to read up on this blowing bridges shit.

The sapper units train how to blow up every bridge in their deployment area. Sauce: was in one

So did you do it by hanging shit off the walls or actually putting explosives into structures?

Everything I find about the defensive strategy talks about “charge pits” and “cavities”, can’t find a single reference to hanging or hooks.

As a dapper you’d use whatever means at your disposal, but as a defensive strategy you’re doing with time, why wouldn’t you actually make pits to put rhe explosives in? I’m sure as a sapper you understand how much more effective it is to have an explosive surrounded by the structure instead of just vaguely close to it, so that a majority of the explosive force actually goes into whatever you’re blowing up. Right?