Abstract: A design method for designing a guide tool including a guide channel for use during cartilage repair in a joint is disclosed. The design method includes: selecting a direction along a joint axis indicating placement of the guide tool in the joint; and placing a positioning mark on the guide tool. The positioning mark is designed to be aligned with the center of said guide channel on a determined joint axis direction and thereby indicating a placement direction of the guide tool in relation to the selected joint axis during use of the guide tool. A design method of insert tools and/or an implant comprising positioning marks and also the guide tool, implant and insert tools designed using this method are also disclosed.