I seem to be having issues attaching images...
basicly a kill box is an enclosed room at the entrance to your base. it typically has a very narrow 1 tile wide entrance which has a corner in it. that way enemies are forced to come round a corner to attack you which robs them of any range advantage. within that box you can place as many turrets as you can fit, just be sure to keep them safely spaced out. you can also have your people ready at the far end hiding behind butchers tables.
Sythers rush ahead and are killed off quick and easy, but the big ones... those require a bit more work and their inferno cannons are a pain in the tail end. which is why you use butcher tables. you can fire over them but not move over them, so if your people are set on fire they don't rush out into the middle of a hail of gunfire X.x stick a door beside the butchers tables and lock it and you have yourself an idiotic colonist proof barrier
Hmm. keep getting Error: Upload path not available
So here's a
Horribly Untrustworthy Link