Grafting a vine from Petit Verdot to Cabernet Franc

Did you ever wonder how difficult it was to graft a vine from one variety to another? Or why that is something that is done? We recently grafted several acres of Petit Verdot over to Cabernet Franc. We are using more Cabernet Franc and actually making two barrels of 100% Cabernet Franc this year! Our vineyard crew had the task to graft these vines.   Here is the process: we took a sliver from the Cabernet Franc vine and attached it to the root stock of the Petit Verdot.  
The piece of Cabernet Franc
Cutting a slit into the root
Inserting the piece of Cabernet Franc into the root stock
wrap the piece so it stays in the root stock
Wrapped up
Cut at the top of the tie so the new piece can begin to grow
It’s a labor of love