Hi!
Retributi0n: As I said before, I strongly recommend having INVADERS turned off initially until you feel ready for a new challenge (the setting can be reset between game sessions in the same fortress, so you can start off with INVADERS off and when you feel your fortress can handle them, you can turn them back on).
Allow me to explain a little bit about weapon traps: Using one mechanism and at least one weapon or trap component (maximum is ten), you can build a single-tile weapon trap. That trap will attack any hostiles who enter that tile. Each time the trap attacks, it attacks with each weapon inside it (so one weapon means one attack, two weapons mean two attacks, ten weapons mean ten attacks). Weapon traps will not hurt any friendlies (dwarves, pets, merchants) UNLESS a friendly falls unconscious on the tile the weapon trap is located, in which case the trap will attack. Note that some of the nastier creatures and kobold thieves have the TRAPAVOID skill, which makes them ignore traps.
Weapon traps can strike an unlimited number of times without any negative effect on the trap. They do not need to be rewinded or anything. However, if they kill something, there is a slight chance that that something gets stuck in the trap, jamming it. In that case, the trap will stop working, but it will immediately create a "CLEAN TRAP" job, which makes one dwarf walk to the trap, and unstuck the object and thereby make the trap dangerous again.
Weapon traps can be stacked with normal weapons (bought, found on dead enemies, created yourself) and trap components. The best weapons you can place inside a weapon trap are bronze or steel cutting weapons like axes or giant ax blades, but for animals, you can also go for menacing wooden spikes which are made at the carpenter's. However, note that armor is very effective at deflecting attacks, so if you want to use the weapon traps to defend against armored invaders, you need to use at least bronze weapons to be sure of the effectiveness. Wooden or glass weapons are absolutely useless against armored foes, it seems.
Deathworks