You can make an attack on the following spokes:
The Hero need to be in range of the enemy, and have line of sight.
When you count the range of your Hero, you use the same approach as when you are calculating the range in line of sight.
Observe specially for attack through slit, that a melee Hero can attack through a slit - and that the range is counted from the Heros position, and that line of sight is calculated from the slits position.