New Trap idea, Electric Wire!

Was going to be unlocked on TH 6, wich gonna be available 3 Electric Wires, it only can be placed in Walls, wich gonna do 5-20 dmg every time that wall is attacked by a melee unit, on TH 8 gonna give you +4 Electric Wired, TH 9 +4 and 10 +6. it upgrade 10 dmg per level or something.

EDIT: WB gonna get hurt only 1 time by the Electric wire.

are they to be hidden? like a trap?

I think its ruled out that u cant have anything on walls