there are kits available at auto stores they usually included a suction cup
some expoxy and a small dimond drill. the theory is that if the crack/hole
is cleaned and suction applied to remove air the expoxy will fill the crack
and become invisable. I have meet with varing degress of sucess on older
cars with these products. clean the crack/hole well and do not touch the
vinyl between the plates of glass. you may save yourself a few hundred bucks
on a new windsheild.>