Too much sun can be harsh on the skin. Some of us are lucky to be sun kissed beauties who can take the heat and still had baby soft skin. Others have chronically dry skin that shudder at the bright light of the horrid sky star.
Umbrellas are usually used to ward off rain, but I and plenty of others use them as shelter from the sun as well. Sometimes you might see this on a beach on an especially sunny day, but people don't stay in one place. Enjoying a day in the market or walking downtown can be cut short if the sun decides it wants to bake you like a poor egg. Smaller umbrellas can be carried around on days like these, but anyone whose town has gotten a sunny beat down for weeks at a time know that sometimes even that's not enough.
If you're sure it's not going to rain, you can add a little fabric to your umbrella to make it even more shady. This is a delicate process and requires to to know a little bit about fabric. Obviously you don't want to choose anything heavy. Even if you're not tired at first, a few hours of carrying your new umbrella + cloth combination will wear you out. Not to mention it's much harder to fold up when you want to put away your umbrella.
You want to to choose something light and black. Black cloth absorbs heat from the sun, and will shield you from it's harsh rays. You can get this same blocking effect from white cloth, but black cloth pushes the fold by absorbing heat from your body. You'll be sheek and cool.
All you really need to attach the fabric it to punch a hole through it it, put it on top of the umbrella and fasten it with a clip.