The India-Pakistan border in Punjab runs about 553 kilometres. Fencing began in the late 1980s and was largely complete by the mid 1990s: a double row of concertina wire, about three metres high, floodlit along much of its length.
It is not built exactly on the boundary. To leave room for patrolling and for the rivers, it sits back from the line in many stretches, which leaves cultivated land on the Indian side of the border but the far side of the fence.
Farmers with land beyond it cross through gates at fixed hours under Border Security Force supervision, with identity checks, and cannot grow tall crops that would provide cover. Sugarcane is restricted in those belts.
The floodlighting is visible from space as a line across the subcontinent.
For the border villages the fence is not a symbol. It is a gate that opens at a certain hour, a crop restriction, and a reason land within sight of a house is worth less than land a kilometre back.
The fence is double, floodlit along its length, and set back from the actual boundary, which is why land belongs to Indian farmers on the far side of it.
Building it took the 1990s. It changed the border from a line on a map into a physical object and it ended the ordinary movement that had survived every previous closure.
Everything about the border districts follows from it: the escorted farming, the absent industry, the drone smuggling, the enforcement presence and the emigration.