Our section of the border, near the Polish town of Terespol, is formed by the River Bug.
We patrol the river bank round the clock, and operate up to 50 kilometres inland.
On the other side they have preserved the old Soviet border regime, known as "the system". There is barbed wire and a strip of prepared earth to record footprints of anyone walking across.
We should soon be installing a chain of cameras sensitive to movement and sensors that detect vibrations caused by footsteps.