I took up a 1/2 in wood floor so I could stain and polish the cement floor. I did not know the door casing was metal and I did not consider the 1/2 in gap that would be left once the wood was removed. I have an idea that I can fill in that gap with cedar (as the photo shows) and then paint the whole casing. My problem is that the threshold gap is a u shape form due to the structure of the metal casing. I would like to make a (u shape) model, that I have no visual access to, so I could then copy it for the other gaps. But I am not sure how to proceed.