For floors that are of different sizes, say a wood floor in one room is 14mm, then you have a vinyl to a connecting bathroom that is 7mm, a normal door profile will not fit as it would be unlevel with a 7mm gap on one side. In this case, you would need a ramp, which is a door profile that curves upwards to account for the differences in length and joins the rooms adequately.http://www.yanghe1al.com/alumi....num-profiles/door-se