Materials: paper 3D glasses, old sunglasses, scissors, scotch tape, tweezers.
Macbook Air unecessary :)
Step 1: Take the Old Sunglasses
Use tweezers to remove the screws holding the lenses in place.
Remove lenses. Clean frame.
Trust me, you NEED to clean the frame :)
Trim the paper 3D glasses to fit the shape of the frame.
Take a piece of tape and cut it vertically into two thinner strips.
Use one strip to tape the two pairs of glasses together at the nose.
Tape the other strip at the end of lenses to hold the two pairs together.
Save the screws to rescue your other sunglasses.
Oh, did I say that's why i wrote this instructable? :)