Modern Trundle Twin Bed.
Trundle beds are for people of all ages, since they are the same as a normal bed, only easy to store. You should leave four to six inches between the bed and the top mattress of the trundle bed. Use wheels small enough so that the trundle bed can fit under the main bed; Make sure the wheels are the same size.

DIY Trundle Twin Bed

Good Trundle Twin Bed Ideas

Great Trundle Twin Bed Ideas

Great Trundle Twin Bed

Popular Trundle Twin Bed

Simple Trundle Twin Bed

Top Trundle Twin Bed