Display setting unknown

Rhino Rhino for Windows
1

Some setting I changed recently results in the square mask over my perspective views. What is it called an where do I turn it off?

Thanks

2

You are seeing your “Safe Frame” (rendering). Go to Options>Rendering>Safe Frame and uncheck the box that says “Show safe frame in active view”.

HTH, --Mitch

3

simple, great. solved.

Thanks