A method for producing an attachment piece (4) which has at least one predetermined break point (16) a cover device for a bone defect site (2) and a device (1) for covering and/or reconstructing a bone defect site (2) are proposed wherein by comparing a first data set which represents the affected bone defect site (2) in the actual state against a second data set which represents the desired state of a bone regenerated at the bone defect site (2) wherein the second data set was calculated or was recorded at a time when the bone at the site now to be regenerated was still a healthy bone (18) it is possible that the regenerated bone which arises through the regeneration of the bone defect site (2) has a form corresponding to the form that the bone at the site to be regenerated had when it was still healthy.
