I have a weird situation with an window extension jamb. The extension jamb is a pre-built frame that goes all the way around the window. I cannot remove the extension jamb frame, but I want to install a stool piece to the jamb. ( I am upgrading the casing etc) My thought was using biscuits to join a bullnose piece to the jamb. The bullnose is about 1 1/2 inches wide.
The problem...I cannot lower the fence of the joiner all the way due to the jamb width (about 2 1/2 inches). What is the technique to ensure the biscuit cuts will line up between the jamb cut and the stool cut? Also, if this is the wrong way to attach the bullnose, please let me know.
Thanks for your time.