For beginners in wine growers. Grafting of grapes. Timing

We continue the theme of the reproduction of grapes.
The author of the video answers the questions of the subscribers of the channel on the terms of grafting grapes into the cleavage (black in black). He explains what needs to be done so that the grafting takes place, the graft becomes accustomed to the rootstock, their required growth is ensured, and the fruiting was normal.
The video clearly shows examples of unsuccessful and successful re-invasions of old grapes.