Step 2: Fulcrum
Tie the too ends together to make a loop,
Center this loop at the middle of the ruler.
This point will be your fulcrum,
If you hold the string the ruler should balance and sit horizontal.
The reason you wrap the string is to keep the ruler from slipping out when it tilts.
Step 3: Building your stand
Bend out the paper clip, and clip it on to the top of the binder
With the paper clip bent out it should make a nice hook to attach items too.
Now hook the string onto the binder. Mess with the string until the ruler wants to be horizontal when it stops moving. (In physics we call this a stable equilibrium.)
When you find your sweet spot tape it down.