IKEA TILLREDA Manual page 19

Upper Basket
Height adjustment
Turn the Rail Stop Clips, at the ends of the
rails, to the sides to open them (as shown in
the image below), then pull out and remove
the basket. Change the position of the
wheels, then reinstall the basket to the rail,
making sure to close the Rail Stop Clips.
When the upper basket is in the higher
position, large items such as pans can be
placed on the lower basket.
GB - 14