[copx]

In normal Rimworld raids enemies only attack walls if you do not leave an open path for them.

That is why meta players always leave one door open. The AI will brainlessly walk in .. right into your kill box.

[kllrnohj]

Rimworld has multiple different raids that defeat that defense, though. Drop pods, sieges, sappers, and breachers - most all in both human & mech variants.

The open-door killbox is still super strong, but you can't survive with only that defense.

[bombcar]

This works in DF also, and with the addition of burrows you don't even have to worry about dwarves accidentally going outside when they shouldn't.