The stock or stub must be cut off squarely and smoothly with a sharp and preferably fine-toothed saw. If one desires to be especially careful in the operation, the end of the stub, or at least two opposite sides of it, may be dressed off with a knife so that the juncture between the bark and the wood may be more easily seen. Professional grafters rarely resort to this practice, however. The stub is then split to the depth of an inch and a half or two inches. Various styles of "grafting-knife" are used to split the stub. The best one is that shown in Fig. 79. It is commonly made from an old file by a blacksmith. The blade is curved so that the bark of the stub is drawn in when the knife is entering, thereby lessening the danger of loosening the bark. Upon the end of the knife is a wedge, about four or five inches long, for opening the cleft. The wedge is driven into the cleft and allowed to remain while the cions are being placed. If the cleft does not open wide enough to allow the cions to enter, the operator bears down on the handle of the knife. The cions must be thrust down to the first bud, or even deeper, and it is imperative that they fit tightly. The line of separation between the bark and wood in the cion should meet as nearly as possible the similar line in the stock. The cions are usually set a trifle obliquely, the tops projecting outwards, to ensure the contact of the cambium layers. Writers usually state that it is imperative to success to have the exact lines between the bark and wood meet for at least the greater part of their length, but this is an error. The callus or connecting tissue spreads beyond its former limits when the wounds begin to heal. The most essential points are rather to be sure that the cion fits tightly throughout its whole length, and to protect the wound completely with an air-tight covering. [Illustration: Fig. 78. Cleft-graft cion.]