posted 06-07- 01:26 AM CT (US)
You can place a hardness tile down on any existing tile and not mess up the original hardness that it has.So to do this press H in the editor and use some keys(not sure which) to select the specific tile you want to place (I'm sure there's a tutorial somewhere that explains it). Then you can either stamp the tile down on any spot on the screen (this does not change the tile's normal hardness).
There's also a way to edit each tiles hardness but the only time I've done that is to fix some errors with the existing tiles and when I added new ones.