Complete Failure! The idea I had read about was to graft heirloom tomato tops to hardier disease-resistant hybrid bottoms. You cut a top and a bottom at an angle and use a flexible silicon tube/clip to hold them together while they join. You keep them in a humidity container for a week or so to keep the tops hydrated until they are getting water and nutrients from the roots.
After a week, more than half the grafted tops had died. After 2 weeks, I removed some of the clips, but the seemingly-healthy tops just fell off. I had 5 left. After 3 weeks, I went to transplant them and THOSE tops fell off.
Well, I'm sure most of that was my fault. It is commonly done commercially and by home gardeners. I know I waited too long to do the initial grafts. The instruction said to do it "when there were 4 leaves" (the seedlings would be about 4" high). Mine were 8" high with 8 leaves.
So I had to use the clips "wrong". Think of an "8" (with a fatter bottom) with a slit cut through the top. The top makes the clip part. Squeeze the fat bottom of the "8" and it opens the top and you attach the 2 angle-cut tomato parts together.
Well, the clip part was too small by then but the fat round part was the right size, so I tried just putting the round part down over the rooted stem and then placing the cut heirloom top down in that. I got them matched in size very well, put it didn't work.
I assume the seedling halves were too old to grow together properly. Or the uncut round part constricted growth.
I'll try again next year following the "4 leaves" instruction more carefully. There are pictures of the initial grafting process HERE.
Fortunately, I made sure to plant enough seeds so that I had regular ungrafted heirlooms to plant out. They are growing well and I have at least a dozen fruits among the 6 plants so far. But the disease problems usually start in August, so we'll see if I get many ripe tomatoes.