Quarter Round moulding is used to hide the expansion gap left around walls during installation.
T moulding is used as a threshold in doorways or as a transition strip where the hardwood flooring meets floor or carpet of similar height. T mouldings can also be used to change the direction in which the floor is laid.
Reducer moulding is used as a transition from the height of the sub-floor to the height of the hardwood floor.
Stair nose moulding is used to cover the front edge of a stair tread or step. If used on a stair, flooring is installed behind the stair nose to cover the horizontal part (the tread) of the stair.