This design for a dual camera rig (see Dual Camera Rig for why you'd want to do this) is based on a T-shaped or L-shaped bracket, washers, and two bolts which fit into the camera mounting holes on most cameras.

You'll need:

• 2x 1/2 inch long 1/4"-20 coarse thread bolts (i bought the kind with grippy heads so i can mostly screw them in by hand, then tighten with a hex wrench)
• a thick rubber washer (mine was called a "Chicago style seat washer")
• 2 cameras with threaded mounting holes
• a 4"x4" T-bracket with 1/4" holes (an L-bracket could work too)
• a hex wrench or whatever you need to really tighten your bolts

Basically follow the steps in the images below:

Be sure the camera is facing "down", such that it will be hung by the base of the upside-down T. I did it wrong at first.

Balance

See how the cameras don't face downward in the following image? In the subsequent image I've tilted them so they actually face down. Do this before tightening the bolts.

Triggering

From here, you can just use a rubber band on each camera to trigger them without synchronizing -- it works pretty well. But if you're interested, I'll be posting soon on how to connect synchronized electronic triggers...