Aaeon SBC-357 Manual page 31

You can use a switch (or a lock) to disable the keyboard. In this
state the PC will not respond to any input. This is useful if you
don't want anyone to change or stop a running program. Simply
connect the switch between Pins 4 and 5. The pin assignments
appear in the following table:
Pin Function
1 LED Power (+5 V)
2 N.C
3 Ground
4 Keyboard lock
5 Ground
Chapter 2 Hardware Configuration 23