In Rogue One, during the Battle of Scarif, once the shield gate has closed, Y-Wings and X-Wings from the Alliance are seen probing the shield by dropping bombs and firing torpedoes at it, to no avail.
They focus their effort on the section of the shield that is within the gate, at great cost to them since that exposes them to the fire from the gate's defensive turrets.
Why did they focus their probing on that specific section of the shield?