A bunk bed is a bed in which one bed frame is placed on top of another, occupying the floor space of one bed and saving space for second bed. That's why it is also called Space Saving Bed. The bunk beds are very popular amony children but as Children move about during sleep and may roll out of bed So it is Not allowed children under 6 years of age to sleep in the upper bunk. Some Bund Beds are joined toghter permanently but its your choice if you want beds that can be separated. Make a decision before buying so that you may not regret later.