http://www.hotrod.com/techarticles/43303/

The Lexan is flat but flexible enough to bend to the stock windshield?s
shape. Holes were dril- led through the Lexan, spaced 6 inches apart, and
sheetmetal screws fasten it to the stock window ledge. Start in the
middle and work your way out, just like you?re torquing an intake
manifold. The Lexan is protected on both sides by contact paper. To
prevent scratching the window, completely fit and install the window
before tearing off the paper.