Laser cut rib cutter as drawn by John Berryman (wordguy on Hip Pocket).
Now back in stock. This is a really nice tool to have.
Price: $25 delivered to the US.
The wood is typically shipped wrapped paper covering at the laser cutter. You need to remove it.
The wood gets taped down – Sometimes this is under the slider itself. I use blue painters tape with some stick removed.
i.e. put on shirt and remove.
Then cut the first cut. Remove excess. Adjust slider and cut first rib. Remove, slide, cut, repeat.