I have a metal prehung door that we installed about 15 years ago. It goes from my garage to my laundry room. I need to replace the threshold before the new ceramic tile is installed and can't figure out how to get the old one out. I removed the screws in it to find that it only released the adjustable part that levels to the bottom of the door. This piece is about 1 inch wide and the width of the door. It was damaged and that is why I need to replace the threshold. After I removed it there is a large gap between the threshold and the bottom of the door. Is it possible to only replace this piece. I can't find the part even after serveral hours of serching the internet. I just started installing the ceramic tile and thought I'd better take care of the door problem before getting too close with the tile. Thanks for any help.