Back in the day when I had a class A motorcoach (8 mpg on a good day) there was always a fear of driving away with the TV antenna extended. There were two ways that folks "reminded" themselves to lower the antenna. The most foolproof way was to hang the ignition key from the antenna handle. When you retrieve the key you would be reminded to lower the antenna. The next best way was to fasten a hair clip to the antenna handle. When you raised the antenna you would move the clip to top of the steering wheel. The clip was a reminder right there in your face.