How do I keep a tension rod from falling down?

r/HomeImprovement posters in our data consistently call out two tricks: set the rod slightly wider than the gap before compressing it into place, and mount on flat painted drywall or tile rather than textured surfaces. Rubber end caps and a 1-inch diameter tube (versus thinner 3/4-inch budget rods) also show up repeatedly as the difference between a rod that holds and one that slides.