Transitions are usually required when a hardwood floor meets other types of floor material or floor-coverings.
While there are some “stock” transitions available to purchase, many are not the right thickness, or are “clunky” in appearance, necessarily being a compromise for a variety of needs.
We prefer to slim down the profile so that the transition is nearly level.
The laminate floor was about 1” higher than the hardwood floor, plus was a “floating floor”, which had to be bonded at the edge of the floor so that a solid transition could be created. We made a solid laminated hardwood transition strip that was then screwed and plugged into place, providing an attractive and solid transition that was not a tripping point for foot traffic between rooms.
Another example, showing the need for a transition from a hardwood floor to a brick mudroom. This was almost 1-1/2” difference in elevation.