This is a simple print that prevents a standard US paddle style light switch from being toggled from on to off or vice versa. Very useful in my case to prevent accidentally turning off a remote controlled light fixture that would lose its pre-programmed hue and brightness levels if the power was lost. 

Can be used in either orientation to keep a light on or off. 

I was able to use the original screws from the faceplate for mounting but your mileage may vary.