Indeed, a hard border. In violation of the Good Friday Agreement. But then again the English never cared much about the island of Ireland.
Which bit of the Good Friday Agreement does a ‘hard border’ violate? From a quick read of https://peacemaker.un.org/sites/peacemaker.un.org/files/IE GB_980410_Northern Ireland Agreement.pdf the only mention of the border is in the context of normalising security arrangements. Putting troops in towers on the border would be breaking the agreement, civilian police/border agency/customs doing inspections doesn’t appear to be.