Shutdown Raspberry Pi through GPIO short circuit

dtoverlay=gpio-shutdown,gpio_pin=3

https://www.stderr.nl/Blog/Hardware/RaspberryPi/PowerButton.html

This will allow to shutdown your pi by short circuit:
GND (pin 6) and GPIO port 23 (pin 16):

Create GPIO listen instance command:

sudo nano /usr/bin/listen-gpio

Set file executable:

sudo chmod 755 /usr/bin/listen-gpio

Create service:

sudo nano /etc/init.d/shutdown-through-gpio

Set service executable:

sudo chmod 755 /etc/init.d/shutdown-through-gpio

Update global configuration - this will read if some changes has been made to startup applicaitions:

sudo update-rc.d shutdown-through-gpio defaults

Reboot and you are ready to use 12mm wrench to shut down your pi: