Do you really need to replace the entire window sill or just a portion of rotted area? I frequently get called to look at "replacing my window sill" only to find out there is some damage to the sill, usually the "nose" area. IF the integrity of the wood of the sill under the actual window is good, then leave well enough alone. First, find the cause of the damage, improper drainage of rain water is the more likely cause. I have cut out and replaced many of the "noses" of a window sill without having to cut out the actual window sill. Some of the newer windows have the two-piece sills and the nose can be replaced easily. Some sills are one-piece construction and can be dealt with. After taking measurements, and WRITING them down, I remove the damaged portion, (thanks to my Multi-Master) make the new piece, trial fit it and prepare for installation. When I put the new piece in I use dowels, an epoxy type glue and finish nails. After all this dries, a good coat of primer and two coats of paint (even if it's the next day) and it's good to go. I've earned a reputation for repairing those *&^%^%$ dormer windows around here as no one want to repair them, just replace them. I particularly don't see why they were even invented, most of them are attached to attic spaces. So who gains from any extra light they let in? My 2¢ worth, David :whistling2: