3. fit the stool (sill) notch the ends of the stool so the portion between the jambs sits against the closed sash. first, cut a rough length of stool (length = outside width of the window + 1-1/2 inches + at least 2 x casing width).. Re: pre assembled casing, separating myth from reality pre-assembly is the only way to go. even if you cut your head casing off 1/16" that is only 1/32" on your reveals. hopefully you aren't off a 1/16" though. i've found if the windows are set out of square, if i pre-assemble i can still rack the casing a bit and make it work.. The vertical side member of a window sash or door panel. stop a wood trim member nailed to the window frame to hold, position or separate window parts. the stop is often molded into the jamb liners on sliding windows. tempered glass glass that has been heat-treated to improve glass strength..
