How Flat is the Keybed?

At the piano, with its action out and keybed clean, apply the flat side of your straightedge to the keybed's front, balance, and back rails for a sense of what you have. Also, check front-to-back at either side and in the middle. This quick gathering of information can serve you well as you try to get your bedding samples to work on the bench, having noted:

1. a crowned front rail,
2. a routed middle area,
3. an odd shape somewhere, or
4. none of the above.

Shape of the Keybed:

Bedding is the foundation of a grand regulation and piano manufacturers put a lot of effort into providing a flat, stable surface on which to construct this foundation. But keybeds, as they age, go through whatever extremes of humidity come their way, whatever neglect happens over time, and whatever unlooked for additions get deposited.