Trundle beds are an excellent way to provide a sleeping area for a guest in your home or for siblings who share a small bedroom. The bed is actually two beds in one: The top bed is typically a twin- or full-size bed, and a twin-size bed is hidden underneath. In old-fashioned trundle beds, the lower bed rolled out and remained near the floor. Newer types are spring-loaded so they elevate the lower bed up to the same height as the top bed. The lower bed locks into place to support a person's weight.
Clear the area of any obstruction so you can fully extend the trundle bed.
Pull out the bottom trundle bed until it clears the top bed. You may need assistance.
Release the latches that hold the trundle bed near the floor area. Latches are typically near the sides of the mattress frame that come out of the space last. Most trundles have a latch on each end of the bed. Releasing them allows the springs to elevate the mattress to the height of the other bed.
Lift up on the bottom bed frame if the mattress does not elevate by itself once the latches are released.
Slide the latches into the locking holes on the top bed frame once the mattress is elevated to the proper height. These lock securely into place and prevent the mattress from lowering once someone lies down.
If you cannot locate the latches, read the owner's manual for the trundle bed. Contact the manufacturer for locking instructions on your particular model.