How do I turn off my solar panels?

I have a 50-watt solar panel that I keep on the roof of my RV to keep the batteries charged when parked at the storage lot. Today I needed to disconnect my batteries while I disconnected and removed my converter for testing.

When I was about to disconnect the batteries, I all of the sudden remembered the strong admonition in the solar panel and charge controller instructions to always connect the batteries first, and never have them disconnected when the solar panel(s) are installed. So I did the removal with the batteries connected, with one partially melted screwdriver as a casualty.

I needed to be able to turn the solar panel "off". But how is that done? Should I have gone up and covered it with a blanket?

Thanks for your help.