Shabbos 22:30

If the canopy of a bridal bed is not a handbreadth wide (about 3”), nor is the area three handbreadths below the roof a handbreadth wide, since it was set up before Shabbos, it may be unfolded and re-folded on Shabbos so long as it does not hang more than a handbreadth above the bed. A curtain for closing a window may be used for that purpose even if it is neither attached to nor suspended from the window since it was designed for this purpose.

Shabbos 22:31

One is permitted to wear a hat with a brim to provide him with shade. If one spreads out the clothes that he is wearing over his head or in front of his face like a tent and they are both tight around his head  and the canopy that he forms is stiff like a roof, then it is prohibited because by doing so he makes a temporary tent.