The bar will stay secured on all surface if it is installed correctly. The only time where our customers is not able to do so is when they have failed to install it properly. Please check- If you have tighten it completely by rotating the middle of the bar. You should reach a point where it cannot be tighten further- Did you secure the bar by pushing the lever down and tightening the screw to lock the bar in place- Did you install the bar in the correct direction.