You shouldn't be defending the horde night base the base should be defending you. Meaning upgrade all walls as much as possible, just mining iron for a day and stone for a couple days will give you enough raw resources for reinforced concrete.

By the time horde night comes around you should just be able to kill zombies without much of a worry, maybe fixing some walls as you go. With either a tonne of bullets and/or some holes to wack through.

I currently wrench a bunch of cars for the brass to make a tonne of bullets (gunpowder and lead is an absolute non-issue since it's so abundant and easy to mine) and stand on iron bars sticking out from the top of my walls and shoot down for easier headshots. Though I'm going to stick a bunch of vault hatch openings in the wall and start sledge hammering to save on ammo.

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Iron spikes can still be very useful, though I now have multiple walls around my base and only have spikes on the inside so that I can max out the XP I get with my own kills, then the spikes help me out if they manage to break through the first wall.

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That's what's worked best for me at least. Though to be honest I'm on my first ever play through (on day 73) and so speaking from limited experience.