Lawdy you could not be more wrong.
Lie them in a straight line in a direction you expect an enemy tank to barrel forwards. Once they drive over five or six (the length it takes to brake even if they're paying careful attention) you'll normally immobilize the enemy tank.
https://www.youtube.com/watch?v=uH8ld-vYQzw has a great showing of them. Game is a little meh in general, but you see the light AT mines put to good use
Where are they man? I didn't see one mine laid down!!!!