Weather Out Flashing's WOF 30 and WOF 40's being installed into a 4 9/16 in. wall opening. Notice that the rough opening is inspected prior to pan installation to make sure that the sheathing is tight to the stud and that there aren't other obstructions that will interfear with proper installation. Also note that the taping tool, which was made from a scrap nailing flange, is used to insure that the tape seals securely into the inside corner at the back dam. If the window or door units are going to be installed soon there is no need to nail the pan in place as the house wrap will hold it temporarily and the window will eventually secure it.