I just removed the baseboards in the apartment that have probably been there since the '50s. The plaster is fine but there are some nails left. I want to preserve as much plaster as possible, so I tried to hammer the nails along the wall. But it doesn't work! It stops completely with 7-8mm left. Pulling out the nails turns out to be equally problematic. It looks like some kind of drive nail. Could it be that there's concrete behind it? Maybe it just requires more force? I'm new to this area, hence the questions.
Not unlikely, there's brick behind it. In my walls, there's often been a nail with a slightly triangular shape, which tends to bend in the wall. If you pull it out, you can expect to take a chunk of plaster with it. Usually, the hole ends up behind a trim, it's not too hard to fix.
If you want to get it out, place a piece of plank against the wall as a support for the crowbar, and pull with all your might.
If you want to get it out, place a piece of plank against the wall as a support for the crowbar, and pull with all your might.