It is probably the most common and easy to achieve of all yolk grafts, it requires that the plant that donates the yolk and the pattern are in the time of full growth, this abundance of sap in the stem makes it much easier to extract The yolk and make cuts.
To perform the grafting, follow the steps shown. The first thing to do is to extract a bud of the plant whose qualities we want to preserve, this bud must have the shape of a shield as shown in the figure. If the plant has abundant wise as has been said, it will not be difficult to extract the yolk with the bark and the cambium attached to it.
Then in the pattern to be grafted a T-cut is made as shown in the figure.
Using a sharp blade, a cross-section is made to the cortex and then longitudinal to form a sort of T, with the blade itself carefully separating the bark from the stem, so as to allow the gusset to be inserted with the yolk.
The dimensions of the T must be sufficient so that the grommet can be introduced completely but not more than that.
This operation will be easier if there is abundant wisdom.
The yolk is then inserted into the T-cut as shown in the figure,
Sliding it gently from the top down until it completely enters the cut, and can be covered with the pattern bark. The figure shows the yolk already in place.
The final step is to cover the entire joint firmly with a suitable plastic tape or raffia, to avoid drying the graft.
Care must be taken not to cover the yolk, it must be uncovered so that it can sprout.
The need to expose the yolk, prevents the total waterproofing of the graft, so there is a possibility that moisture can enter the union and with this can occur the proliferation of fungi that ruin the graft. This possibility makes the use of waterproof plastic tapes not indicated when the grafts are made on the outside and can be moistened by rain or irrigation, in these cases only recommends special tapes sold for that purpose, these tapes (Raffia) allows some transpiration and with it the exit of the moisture of the graft.
A variant of this method is called the inverted T, which in essence is the same, with the difference that the T-cut is done in an inverse way, ie with the cross-section below and the upward longitudinal cut
Source: http://www.sabelotodo.org/agricultura/reproduccionvegetativa/injertos.html#Institutos_de_yemas