Hey there I've been working on a this project on and off this summer. (mostly this fall)
As you can see it's A hidden blade, I started with a ,desk drawr slide ,some sheet metal (For the blade and part of the trigger mech) ,a few nuts and bolts ,and some thick steel wire. also a paper clip or 2 bent into some small springs.
I'll be building 1-2 more after i finnish this one i'll be making an instructable for those. This one's kinda the test dummy.