I'd caution people not to expect the wedge system of cutting to prevent saw-jams. I used to cut a wedge, from my earliest days, but you still have to make a first cut of the wedge, and that one used to jam the saw. Sometimes it was the back-cut from the reverse side that jammed the saw, after the wedge was cut. It was the wedge having been cut out, that caused the middle section to be fired out sideways when I made a second cut above the first one. (I didn't have any kind of winch to pull the tree over, it all had to be gravity.)
Never, never cut, or trim a tree that is already down, from the downhill side, even though it is often much more convenient to do so. The reason it matters for trimming, is that it isn't uncommon for the tree to roll when you trim it, and it is very difficult to predict. I used to know a guy who was a quadraplegic due to that happening to him. (He felt he just had to clear his driveway in the middle of a night-time thunderstorm, when a tree fell across it. Of course the tree rolled on him, pinning the back of his neck.) I also had one experience where I was trimming a fallen tree - from the uphill side, I'm not that stupid - when it suddenly rolled, taking the chainsaw with it. It rolled 20 metres down a very steep slope and came to rest with the saw still jammed in the branch and still running. Think first, and be careful!
