Eek ...two pole switches
I once worked in a research lab where one day a Hit Team of electricians arrived ... to rip out two-pole switches and replace them with switches which only switched the live.
Why the panic?
Well, with a single pole switch failure either the equipment stays on - or stays off.
With a 2-pole switch you can get the live side blade stuck ON ... so when you turn the appliance off ... it STILL has a live feed! The switched neutral line is doing all the switching!
Lethal!