Transition line items are length-based and mostly applied at doorways where the different room coverings transit. Also the transition item can be drag-and-drop to any wall section.

 

Apply Transition at Doorway: simply drag the transition item from the material panel and drop it over the highlighted doorway.

 

 

Apply Transition at Any Wall Section: simply drag the transition item from the material panel and drop it over the wall base (even to open wall base, i.e., the line segment with wall removed) to count for the length of the transition material usage.