mechanical brake switch

[Wynand]

It depend if you have hang down or floor mounted pedals. And each method have different options based of space, design etc.

That said, I built my own floor mounted pedalbox and here is how I fitted mine - when the pedal was cut, a notch / cam was left for the switch activation.
I had to keep the switch in line with pedal for the bias bar push rods (not fitted in pics) to clear
Here are some pics of that.