YouTube user Moonyjube posts a video in which they use a manual temperature control (a human with a switch) to moderate the warmth on their heated print bed. Why on earth would someone use manual feedback? Haven't they installed the appropriate and commonly available hardware to do this automatically? The answer is found on the video:
Because I can't get the *****ing Mosfet to work.
I have to keep turning the heat print bed off and on our own to maintain a stable temperature of 110C. By hand!
Such is the life of the hobby maker. There's always a way to get it working, even if you have to do it yourself. By hand.