This is not a weird version of tic tac toe, I’m actually getting ready to level the keys.
The black and white keys are specified to measure a particular height all the way up and down the keyboard. Often, from years and decades of use, the height can become skewed, resulting in an uneven appearance. In severe cases, it can drastically alter the playability of the instrument.
The little colored round things, called punchings, are placed under each key. Each color is a different thickness, to accommodate various heights.
Way back under the key, this punching needs to go underneath the red felt. It’s a very tedious process, and, depending on how much leveling needs to be done, can take quite a long time.