I have seen a few variations on keys. The wood bow ties that are mortised in cross-grain to prevent further splitting of a crack in a slab of wood (aka dutchman). I’ve seen dark wood keys in light wood, light keys places in dark wood. I have seen fancy carved keys in the shape of a wineglass, butterfly, an X, and dragonflies. I lack the patience and skills to carve fancy shapes and mortise the place for them to sit. But I did decide to have a little fun anyway. I wanted to try some keys that had straight lines for cutting and mortising, but still had some curve to their appearance.

First I took similar pieces of walnut and cherry then taped the two blocks together with double-sided tape.

I then traced a curve using a flexible curve tool and cut the path on my bandsaw.

Ready for some mortises to call home. The bottom keys were freshly planed, so the cherry looks lighter.

These two will do a good job of stabilizing the crack in the slab, while the slab goes back to dry for another 8 months.
I enjoyed making these and am happy with the visual effect they have on my project. It was a pretty simple method for softening the look of the standard keys. I think they might add a nice effect when you have two cracks that are side by side. The keys could be made so that it looks like the curve flows from one to the other. One nice thing about this approach, unlike some fancier carved keys, is that there is virtually no degradation of the strength of the key.