My friend Tim Hoehn-Boydston has an extensive collection of Ficus trees. One that he has in his collection is Ficus benghalensis. He has two forms, one with normal large leaves and the other with much smaller leaves.
Tim decided to graft the smaller leaf form into the large trunk of the larger leaf variety. This would put smaller leaves onto a larger trunk specimen; always a desirable featue in a bonsai.
Three grafts were placed. The top one was an approach graft bringing a long branch of the small leaf tree and placing it into a groove in the top of the large trunk, large leaf tree. Two other grafts were placed lower on the tree and these were free grafts not attached to the parent tree.
Baggies were closed around the free grafts as a humidity measure to keep these small grafts from drying out while the grafts took. Baggies are removed in several weeks when the grafts are showing signs of taking.
The top approach graft is kept in place until the graft shows signs of growing strongly and then is severed away from the mother tree.
Grafting is one way to introduce better foliage on a tree.