I'm trying to document putting one of these together, since it's not in the instructions.
First, get one bicycle cable, one thick trigger support, one thin trigger support, and one finger. Here's the cable and thick part:
Put the end of the cable with the ring on the end into the curved groove like this:
Put the thin part on, and drill a 1/8" hole:
Screw together gently with a 3/4" wood screw:
Put the finger between the supports like this:
And use a bolt and nut (gently tightened) through the holes:
Finally, drill a 1/8" hole in the finger to the right of the cable and as high up as you can, and use a 1/2" wood screw and a small washer (washer isn't in the parts list, just find a relatively small one) to squeeze the cable between the finger and the washer:
OK, so if you unravel the bicycle cable now, you should be able to pull on the other end and get the finger to press downwards. It should be a relatively simple task of mounting your cameras, finding the best position for the trigger support, and screwing it into the camera mount. You can use the mini bungee cords (they're about 6" or 8" long) from the bungee cord assortment (if, that is, you got it from Home Depot), and attach them to the curved section on the right side of the finger.
For the other ends of the cables, you need to attach those to the dual cable bicycle brake lever, and unfortunately I haven't figured out how to do this very well. Perhaps someone who has built this can explain?