Window Plate (one of two). This is just sheet metal from the hardware store. It was 12"x24", which is the PERFECT size to fit over the window. It covers the open window and the middle frame of both the upper and lower windows when the window is open -- you don't see the window slide-locks or the top frame edge of the open window.
I drilled a 3/8" hole to get my tin snips started, then cut most of the center of each hole out, leaving a bit to fold back over so that I didn't have just a flat sheetmetal edge. This allows some bearing surface for the stovepipe (the curved part where the little tabs are folded over.)
One plate goes inside, and one goes outside. I located my holes and drilled the sheet metal before painting it with primer and white paint (not hi-temp paint, just regular cheap spray can paint.)
