Is this some kind of smut talk code?
If not, then the word you want is słupek.
If you're asking about building regulations then nothing anyone on this forum can tell you about where to your fence is worth anything. The only answer that matters is what the local authorities where you live say.
If it _is_ dirty smut talk then put your fence post whereever you want to, just spare the rest of us the dirty details.....
if we are taling building laws- your fence has to be on your property. If it's fence between two private properties, you don't need any paperwork, but you can cooperate with your neighbour, who can allow you to put half on your side, half on their.
If the border is with public place, like a road you need paperwork, and you have to stay 100% on your side of border. I sugeest hiring someone to make a fence and help you handle paperwork.