Tri fold closet doors
Interior Doors and their classification of way of opening : Tri Fold Closet Doors
Quote from Article entitled Interior Doors and their classification of way of opening:
They are one of the single swing door types and this door took its name from a place of an original use. Doors, consisting of two halves (upper and lower), with their locks and hinges were used in stables and now become extremely popular in apartments especially in the west.Such doors are suitable if a family has small children or pets. A lower half-door blocks the way and an upper one can be opened for airing. Stable doors look especially seamless in a kitchen.
The full version of the article can be found here.