Marking out a log for sawing

So I am I working on the woodshed, and we have been squaring timbers freehand with a chain saw. I thought it might be of interest to outline the marking-out process. I have only found one place where someone tells you how to do this. That is the invaluable Will Maloff's book Chainsaw Lumbermaking. This book is out of print, and last time I looked it was around $70 in used-book markets. Not a trivial investment.

Marking out is not at all hard but it has its, erm, flats and sharps. You will need a level and a felt-tip pen or soft crayon. The level is better if it is longer. OK, look at your log and decide where the center of the thing is. There are, surprisingly, two alternatives. You can mill to the heart of the wood or you can mill to average center, or center of mass. In my example I will be milling to both at the same time, because my spruce is symmetrical. More or less.
So take your pen and put a dot at the center. Then with the level you strike a horizontal line across the log, as above. Hold the level vertical (you could use a plumb line, too) and strike a vertical line. You now have a coordinate system established, with a level axis and a plumb axis. Now with a square, a ruler, or whatever, mark out your corners. A square is much better than a ruler because you can mark square to the reference axes. I use a Japanese framing square. Much neater than cumbersome western squares. But any square will do the job.
Now recheck your measurements. I spotted (and you can spot) an error immediately. Measure twice, cut once. The opposite strategy does not, repeat not, work. So once your measurements are correct and checked, draw the square (or whatever) on the end of the log.
Now move to the other end of the log, which you have, of course, held securely so it doesn't move. I will come back to this. Repeat the process. Do not let the log move because if you do, you will have lost level and plumb.

At this point I forgot to take a picture, so the pictures will go in out of the actual sequence. You will need a chalk line. This is an inexpensive gadget, basically a string that gets dragged through some powdered chalk, with a reel to hold the line. The reel, by the way, makes a dandy plumb bob. Following Japanese practice, I took a short piece of branchwood and sunk a sharpened nail into it. The line is held taut by the weight of the reel. Modern reels are made of plastic, and are very light. If you can find one, the old steel reels work much better. I have two.
The peg and its nail are driven in at one corner and the reel is adjusted to fall over the corner on the far side of the log. Perhaps you should cut out a notch with a knife, to make sure it really stays put. You now have a nice straight line. Notice that the log is spiked down to the hewing bench, which is holding the whole thing up, by a homemade log dog, a giant staple. This preserves level and plumb. There is also a flat side on the log. That's where I forgot to take a picture. Go to the middle of the log, pull the line out and let it go. It will snap back and give you a nice straight chalk mark where you must saw. Now saw your scoring cut right down the chalk line and go for it. I described this a couple posts ago.
As you go on, constantly refer to your level and plumb marks, or you will have a rhomboid and not a rectangle or square. If you have to, use wedges to preserve level and plumb. For smallish logs like this, I far prefer the freehand method to using a chainsaw mill. But even if you do use a chainsaw mill, and I may get to that yet, marking out makes the difference between a hack job and something halfway decent, and the marking-out process is very similar. I am using Parsifal, a Stihl MS170, the smallest Stihl in the inventory. It is beautiful on ripping cuts. It has a very narrow bar, small waste, and even without a ripping chain it makes perfectly adequate cuts for my purposes, since I am building a woodshed and not cabinetmaking. Of course you have to keep the chain sharp, but that's another post.