The invention relates to a wheeled carrying structure with collapsible undercarriage provided with a carrying frame, two supporting wheel axles； both with at least one wheel, which are connected with lockable swivelling legs to the carrying frame for moving the supporting wheel axles between a mobile position at a distance from the carrying frame and a collapsed position located near the carrying frame. The invention also relates to methods for moving a wheeled carrying structure of this kind between a higher and a lower base.
