A trundle is frame that is often used as a bed and is conveniently stored underneath a day bed or bunk bed. For those who have guests sleep over from time to time but don't have the room to set up an extra bed, a trundle is a space saver. When not needed for a bed, the mattress can be removed from the trundle and clothing or other items can be stored there.
Identify the parts of the trundle. There are two side rails, two end rails and around 10 slats.
Set the two side rails on the left and right so the screw slots in each rail are facing inward. Position the end rails at the top and bottom in between the set of side rails.
Connect the end rails to the side rails with either a dowel or screw. Use an Allen key to tighten the screws.
Arrange the slats in a line, oriented by width, in between the side rails. Use the Allen key to screw the slats into the side rails.
Place the mattress over the trundle after all pieces are screwed in. Turn the trundle so the tallest side rail is facing away from the bed. Then push the trundle underneath the bed frame.