Shaped exactly as its name suggests, T-molding is a quick and simple solution to covering the gap between two materials and creating a threshold. The T's vertical part slips into the joint between the two floors while the T's horizontal section rests on top of the two flooring materials, creating a transition point that serves as a threshold. T-molding is installed with construction adhesive from a tube and simply slipped in place.
Mable thresholds install just like ceramic tile. While most of the time they can be bought pre-cut and ready to fit the majority of residential doorways, sometimes it's necessary to cut them down to size with a tile wet saw. Thin-set mortar is applied with a notched trowel to the back of a marble threshold and the floor, and the marble threshold is pressed into place. After the mortar dries, the marble is a solid threshold transition.
While less common than marble thresholds, wood also is used to create threshold transitions from material to material. The easiest way to install a wood threshold for wood flooring is to do so during the floor's installation so that you can use scrap material and have all of your tools accessible. This approach allows you to nail and glue the threshold in place with the rest of the wood floor.
You can create thresholds from scrap pieces of ceramic tile, or you can cut pieces of tile to fit based upon your desire for the threshold width. The installation should be done during the ceramic tile project, with the threshold pieces set in thin-set mortar along with the rest of the tile. Once the mortar dries, you can grout the threshold pieces in place with the rest of the tiles' installation for a finished threshold.