u/KomendantJPEG

There are no border signs nor lines to notice, and only the changed quality of road was the obvious sign of entering into the different country.

... And the estate where you can almost literally jump into another country out of your window. In fact, it'd be much more logical for the local residents to buy groceries in the Polish supermarket (which they most definitely do) and pick up their parcels from the Polish pickup boxes (which they probably don't do) as they are all located closer or even much closer than the Czech ones.