A method for producing a top attachment of a covering device for a bone defect site , the method consisting of the following process steps: - recording a first data set which represents the involved bone defect site in its current state, - comparing said first data set with a second data set which represents the target state of regenerated bone at the bone defect site , the second data set being either obtained by calculation or having been recorded at a time when the bone at the site which is currently to be regenerated had still been healthy bone , - utilising said first data set and said second data set for the purpose of planning the top attachment , which has a wall facing away from the bone defect, as well as a wall facing towards the bone defect, and which is suitable, if and when necessary, for being fixed onto a bone by at least one fixing means , - implementing the planning of the top attachment in the form of a planning data set, and - supplying said planning data set to a manufacturing process, in particular to a computer-controlled manufacturing process, in which the top attachment is made of a dimensionally stable material and its wall facing towards the bone defect or its wall facing away from the bone defect corresponds to the shape of the regenerated bone in its previously determined target state, wherein concurrently with the manufacture of the top attachment at least one predetermined breaking point is disposed on said top attachment which is designed for removing said top attachment and wherein the top attachment is dimensioned in such a way along an opening that forms upon breaking of the predetermined breaking point , that the top attachment may be flush with the healthy bone adjoining a previously determined bone defect site . - recording a first data set which represents the involved bone defect site in its current state, - comparing said first data set with a second data set which represents the target state of regenerated bone at the bone defect site , the second data set being either obtained by calculation or having been recorded at a time when the bone at the site which is currently to be regenerated had still been healthy bone , - utilising said first data set and said second data set for the purpose of planning the top attachment , which has a wall facing away from the bone defect, as well as a wall facing towards the bone defect, and which is suitable, if and when necessary, for being fixed onto a bone by at least one fixing means , - implementing the planning of the top attachment in the form of a planning data set, and - supplying said planning data set to a manufacturing process, in particular to a computer-controlled manufacturing process, in which the top attachment is made of a dimensionally stable material and its wall facing towards the bone defect or its wall facing away from the bone defect corresponds to the shape of the regenerated bone in its previously determined target state, wherein concurrently with the manufacture of the top attachment at least one predetermined breaking point is disposed on said top attachment which is designed for removing said top attachment and wherein the top attachment is dimensioned in such a way along an opening that forms upon breaking of the predetermined breaking point , that the top attachment may be flush with the healthy bone adjoining a previously determined bone defect site . <EOS>