These are hardwood flooring transitions - we use these on every single flooring job. The first picture illustrates a stair nosing, as implied they are necessary when installing hardwood over steps. The second illustration is of a hardwood floor reducer molding. Reducers are required when hardwood floors meet other flooring at a lowered height. The third picture is of a hardwood flooring t-cup molding. T-cup moldings are required when hardwood flooring meet other floors at equal heights.