I had a fair number of people asking me how I made the borg arm for my Vriska cosplay, so I went ahead and made this tutorial thing. Here's to hoping that people find it useful! Now, I know that this tutorial is very poorly arranged, so if you've got any questions, fire away and I'll answer as best I can. And if you do anything with this, I'd be thrilled to take a look at it!
I used a couple of tutorials for this myself, specifically Anniina85's stocking arm tutorial and Amethyst Angel's plastic automail tutorial.
EDIT: Oh man, this thing is so full of typos. I'm gonna have to fix those at some point.