NevilleChaimBerlin: You remind me of the old joke ” whom do you believe, me or your own eyes?”. AviK brought down explicit sources for the hetter of an umbrella on Shabbos and you deny they exist. True, today, it has become acceptable not to use an umbrella or parasol but that is a chumro , accepted by the klal, not an halocho.
And you are totally wrong about ohel. We pasken there is NO din ohel by keilim, only mirabbonon in specific cases. Check it out.