They hung up trees with ropes about 10 kilometers from the Russian border to hide the road from airplanes.
It looks like it’s not enough to cover the road but, when the road was viewed from an angle (not directly above) and a high altitude, the trees concealed enough of the road to make it difficult to identify as a road.
Source for original picture is The Finnish Wartime Photograph Archive
80 year later and the Kremlin is still out there murdering people for land.