How in the world do you use the Nailgun

[Althamus]

Or into their legs/ the floor in front of them. That way the nails will bounce off the floor and off the ceiling. :]

Eh. Less effective in most cases.

For the nails to hit the zed twice, you'd have to be very close to them, in which case it'd kill the zed, but probably leave everything behind it unhurt, losing the whole shotgun point.

Unless you're scrake killing this way, it's probably not really worth it.