Grafting is placing two cut surfaces of one or different plants under conditions which cause them to grow together. In cleft grafting the stock has to be split open by a chisel or other instrument. The scion is cut wedge shaped and fitted in the cleft so that the inner barks meet each other.
Nicholson, George The Illustrated Dictionary of Gardening, Div. VI (London, England: L. Upcott Gill, 1884)