Transition Pieces
Catch-all term for T-moldings, reducers, thresholds, end caps, and stair nosings used at flooring boundaries.
Transition pieces handle every place where flooring meets something else: a different flooring material, a higher or lower floor, a doorway, a stair edge. Common types include T-molding (same height adjacent floors), reducer (different heights), threshold (under a door), end cap (terminates against a wall or sliding door track), and stair nosing.
Transition pieces are typically priced per piece (not per sqft) and run $15-$50 each for stock options, much more for custom-finished or hardwood options.
For a typical residential install, count every doorway and floor-type transition during measurement. Underestimating transitions is a common margin leak.