Because the folded over piece is exactly half the width of your router base, your router will be perfectly centered.
This photo is part of the Centering Router Dado Jig album and was taken in Des Moines, Iowa with a Google Pixel 3.
It's also on Flickr.
I've got 17 photos from this spot
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The beauty of this is:
1. That you only measure and operate on center lines. You never have to find the edges and make sure you're on the right side of the line, etc.
2. That this jig will work with whatever size bit you throw on the router.
And that's it.
Derek Brooks posted