“They could at least put up some temporary gates!”
In urban areas, they struggle to temporarily block gaps at the end of the work day, and reopen them at the start. But far out in very rural areas, they save the time and effort for getting the permanent barrier up.
When they do leave a gap for the gate crew to fill, sometimes they do block the gap with some of the old barrier, like the Normandy style vehicle barriers. Sometimes though, the gap is actively used by Border Patrol or other workers, and left in drive through condition for them.
Unmanned Ground Sensors (like a game camera that alerts at the command post) can be placed to monitor those gaps. The guys on shift can post a guard, or keep patrols nearby - It is still a much more defensible condition than existed just before the new bollards came through. In the meantime, its an opportunity to channelize intruders, for easier ambush.
In the meantime, its an opportunity to channelize intruders, for easier ambush.
Like herding cattle, sheep or pigs into a chute to control and direct them.