I am attempting to make use of traps for the first time, I read the wiki but it didn't answer a few questions. First off, if I put down traps and the merchants go over them, will they trigger the traps? Second, it says wood is possible to use for certain trap components, but is this worth doing? Lastly, How frequently do weapon traps jam? I ask because I plan to put some menacing spikes in weapon traps outside the walls and don't want to put my mechanics in too much danger if they are unreliable.
Merchants won't go over traps, at least wagon won't. I've not tested with pack animals since wagons have better capacity and traps blocks depot access. Traps won't activate on anything friendly, unless they've been stunned, unconscious or webbed ( creature that shoots web doesn't get webbed ). Diplomat can 'disable' traps for their civ unless you rebuilds them, if they goes over it to talk to your dwarves.
Wood's worth it if you don't have anything better yet.
Weapon trap jams half the time if they get a killing shot, corpses get stuck inside of the trap and dwarves will come to unjam them. That's why blunt trap like spiked balls are popular with some players, they get killing shot a lot less often.
Menacing spikes can be linked to a lever and toggled by some busybody, They won't jam if remotely activated, it'd have to be set as upright spear or spike, I forget the wording. Then linked to a lever, and so on.