How To Survive 2

The first trap you can build is the Rotating Arms trap. Your camp must be level 11, and you will need the following items to craft it:

Wooden Board x3 - The "Rabid Coyotes" quest has a lot of these, or you can make them with a big piece of wood (found everywhere) and a Saw (found in "Warring Brothers")
Braided Rope - The "First Time in the City" quest has a few of these, and they can spawn in the house to the north-east of Kovac's pylon (your starting point)
Box of Nails x3 - Found everywhere, especially during city quests, Kovac's vault, or by crafting at your Foundry
Hammer - The "Helmet of Discord" quest is a good place to find this

Then just put them up where you can find a lot of zombies. The camp challenges are good for this.