Here is one style of hang ons that I make. I call it a leg stand being its got a longer leg on the bottom that I use to adjust to crooked trees so the stand is still in a level position.
Over all picture of the stand.
You can see how the chain set up is and how I connect the chain.
Here's the spike that goes into the tree on the leg part of the stand.
Here you can see how the leg of the stand is able to swing to adjust to the leaning of the tree if it was growing at an angle. Where the leg connects to each side of the stand is a small rod that is wleded in between the frame. The leg part is a pipe shaft a tad bigger then the rod so it can swing freely when I move it.
You can see the spikes that hold it in the tree. These are grade 8 bolts that I sharpened the ends on and welded to the back frame of the stand.
Pictures really don't do justice here. Its one thing to explain it and post a picture and another to see it 1st hand. Some of these stands are 20 years old, I've had a few welds come loose but hardly any. Always keep a close eye on your portable stands whether they are store bought or homemade.