You are a hard-core ping-pong wizard. You apply copious spins to every shot. People are impressed with the seriousness of your regard for the sport that is table tennis.
Then you leave your paddle in the trunk of your car. The once soft and sticky rubber (that is so crucial to your game) melts into the foam betrayal of the case that was meant to protect it. You remove the rubber through razor blades and sandpaper + elbow grease. You order new rubbers from the internet and patiently wait, looking forward to the future schoolings you will give your colleagues.
Wait a minute... you curse, you realize your paddle is a bit warped now. This injustice prevents you from sleeping well. You cannot stand the thought that this once noble implement, the extension of your will and motor function, is not as perfect as it could be.
So, you resolve to bring it back to its former glory.
Step 1: How to make a not-flat thing flat
How do you make a non-flat thing flat? You can perhaps surround it with flatter things, hoping that they will persuade your non-flat thing to become a flat thing. You consider what kind of flat thing would need to exist to to make this happen. One option is to buy a ready-made flattening thing, such as the Yasaka Clicky Press. But, you don't want to wait to castrate yourself with such a thing, when you know you could make the same thing in like an hour with a trip to Home Depot.
The basic design is Flat thing + Flat thing. You remember that trees are a source of flat things, and you go find some cut trees. You choose oak, which is a nobler and stiffer flattenerer at like $9 for a couple of feet of 1"x8".