The Haddon Lumbermaker is a chainsaw attachment that turns your saw into a small portable mill, for cutting boards, planks and beams right where the tree falls. It fits all chainsaws and attaches to the bar in seconds.
A 2x4 or 2x6 nailed to the log is the guide board, and the Lumbermaker rides along it to keep the saw cutting straight. A 2x6 gives it a wider surface to ride on and more precise work, and a log 9 in across will square up into a 6x6 timber. It works with regular chain, the saw swivels for plunge cuts, and it also guides straight cutoffs. It's made in the USA and comes with a 30-page how-to manual.