The cutting guide (1) has a guide main structure comprising a sagittal guide plate (10) that is oriented relative to the bone. The sagittal guide plate has two sagittal guide slits (12) for guiding a bone-cutting tool. The sagittal guide slits are extended through sagittal guide plate and are arranged at an angle to each other. A transverse slit plate (20) is arranged perpendicular to the sagittal guide plate and is provided with guide slots (22).