A.Kevin Vilhauer, a design engineer and manager of testing and R&D at Milgard Windows & Doors, responds: Other window and door manufacturers may have a different policy, but installing Milgard products with either pneumatic coil nailers or narrow-crown staplers will not void the warranty. The most important thing is to maintain the integrity of the nailing flange around the outside of the frame, which also serves as a water barrier. If the flange is damaged, the window’s warranty can be voided (though a damaged flange can also be repaired). One advantage to installing vinyl windows with a nail gun is that it’s less likely that an errant hammer blow will strike and damage the window frame. Just be sure that the pressure is properly adjusted so that the heads of the nails or staples don’t penetrate the flange, and use corrosion-resistant fasteners.