A technique is presented for interforaminal lateral augmentation of mandibles with adequate bone height, but extremely knife-edged mandibular alveolar ridges (Class IV of Cawood and Howell's classification of residual ridges), in which the crestal portion of the knife-edged ridge is used as grafting material. Following an osteotomy and rotation of the grafts by 180 degrees, the grafts were fixed to the residual ridge below the osteotomy line by means of miniscrews. All grafts showed only mild resorption after a healing period of 3 months, and it was possible to place 4 implants in the now sufficiently wide host region. Keywords: augmentation, implant placement, knife-edged ridge