The "soapy string" trick -- a classic to be sure. Modern windshields are held in place using very strong adhesive, but not too long ago they were installed using no adhesive and only the rubber held the whole thing in place. It was a good system, and ultimately easier to replace a damaged windshield. The hardest part of this installation was getting the rubber windshield gasket to pop over the lip of the car body so it would hold the windshield firmly in place.
This is where the soapy string comes in. Soapy string isn't a snappy euphemism -- it's a string drenched in soapy solution. And it works.