Each guard at the crossing point carries a device linked to an international database – one swipe of a passport and the holder's details come up on a screen.
You can see immediately if someone has been barred.
We have detected 55 forged Schengen visas so far this year.
On rare occasions people try to cross the border hidden in vehicles or trains. Mainly they are alone, or groups of two or three. Organised trafficking of migrants is a much bigger problem further south, on Poland's border with Ukraine.