In the 80's I had a house built in Sarasota. Every room opened to Lana. The glass sliding door threshold was flat. When I see/ask for/currently have has about an inch raised track. I assume because that door goes directly outside and does not let rain onto the floor. I would like to have the level threshold as Edi is having some trouble at times lifting left leg due to back injury. The sliding door will go from house to lanai. Thanks