Imagine trying to cut these joints in timbers:

Now imagine trying to cut those with a chainsaw. It would be impossible—freehand. Thus Lignatool, an Austrian manufacturer of woodworking tools, developed this jig. It's called "Schnittführung für Kettensägen," which translates to "cutting guide for chainsaws."

Note that the steel band mounted above the blade acts like a riving knife, ensuring the cut doesn't close when you're in the middle of it. This makes kickbacks and jamming virtually impossible.

The chainsaw can also be mounted perpendicular, allowing you to cut tenon cheeks.

They also say they sell an adapter for cutting non-S4S logs (though I couldn't find an image of it on their site).

The company makes models to accommodate two different bar lengths; you provide your own chainsaw. Prices run from € 2,143 (USD $2,336) to €3,023 (USD $3,295).