The outline of the grafts is traced with a side-cutting burr or a saw.
The initial grooves are deepened to the level of the diploë.
The diploë must be visible, which is indicated by cancellous bone bleeding.
A trough is created along the side of the bone graft by tangential saw cuts. The outer edges are beveled smooth to give a flat access angle for an osteotome and thereby permit calvarial splitting.
The outer cortex grafts are separated from the calvarium by sequential advancement of thin osteotomes through the diploic layer.