Forum:Spell speed

i'm confused with spell speed. if a person is to attack me and i activate scrap iron scarecrow then they use seven tools to counter i can't activate another scarescrow or similar trap to negate the attack? but i rememeber if my first trap fails i can activate magic cylinder during the what's called battle step(it asked me if i wanted to activate dring battle step in GBA) why does this happen. Or am i just completely lost and wrong.