I have no idea what it's called but I'm curious why most pianos have a flat section to the left of the keys, and what it's called.
It almost looks perfect for resting a cup of tea on which sounds like a horrible idea unless you want sticky keys.
Music: Practice & Theory Stack Exchange is a question and answer site for musicians, students, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
As @BobBroadley says, the Key Block holds the keyboard in place. However, why is the key block needed in the first place? Presumably the left side of the case could do the same job.
Key blocks have been a part of pianos since their invention. The article Who invented the piano – and why does nobody remember him? includes a (copyright controlled) image of a Cristofori piano, clearly showing key blocks at either end.
The why is that room for the piano's frame is needed between the action and the case. Pianos are not mounted directly on the case, rather the frame rests inside.
Upright / Vertical
In addition to leaving room for the frame, extra room is needed on modern pianos to account for the diagonal placement of the strings. The strings in the piano are set at an angle, which allows for greater string length without lengthening the entire instrument. Because of this, there's extra space at the end of the piano.
Here's an interior view of a typical upright piano (an Essex). Notice how the bass strings extend past the left edge of the keyboard.
In fact, one can see that the action itself is angled to the left., and there is also room for the frame and some of the pedal mechanism. Thus, the key block is a necessity.
The situation on a grand piano is the same. First, there needs to be room for the plate (frame) between the case and the action. In addition, due to the angled strings and the hammer strike point (shown in the picture below), there needs to be some extra room for the strings to meet the pin block.
(and, yes, putting a teacup there is a terrible idea. )
I'm a professional piano tuner, and can confirm that this block is provided by the manufacturer primarily for your drink and cigarettes.
The overstringing bit was an afterthought, they wondered what to do with the extra space the so-called "beer and fags shelf" created so they angled the bass strings to fill the gap.
They are called key blocks. They hold the piano keyboard in place.