Circuit Board Design Class
It does matter which wire is which. You want the switch to control the hot not the neutral. Otherwise the entire circuit is electrified and waiting for a completion, which could be a person if they are not careful. Which wire matters so much that new plugs all have a thicker side for the neutral to keep the polarity correct.
Do you find the weight to be heavy enough? I don't know what a pole barn nail weighs. Most of the bo shuriken I've used from Japan are surprisingly heavier than you might imagine. Of course, those might have been for dealing with different armor / clothing / distances than you may need for these.