Abstract: The invention relates to a method for precisely-positioned production of a cavity, especially a bone cavity, at a preparation point by means of a hand instrument, comprising the following steps: calculation of position-dependent surface characteristics from a three-dimensional data set of the surface of the preparation point at a desired position of an implant which is to be inserted in said cavity, wherein the area in which the cavity is to be created is represented in the form of a three-dimensional data set of volume data; detection of at least one partial cut-out of the preparation point comprising an actual visible surface feature by means of a camera which is arranged on the hand instrument at a pre-defined distance to a processing tool and display as a video image; insertion of a calculated surface characteristic for the desired position of the hand instrument, wherein the inserted surface characteristic can be altered, especially made congruent with respect to its position in relation to the actual vi