Use sunscreen or sunblock

This afternoon, I'm at a ball game. No surprise. My grandparents show up. No surprise. My grandpa wraps his left forearm in a towel. Whoa. What is the towel for? During his many years driving trucks with his arm resting on the rolled down window, he now suffers from skin damage. He gets a burning sensation and pain from exposure to the sun. His skin there is thin and bruises very easily. So geocachers, learn from my grandpa and protect yourself from the sun. Even filtered through the trees, the sun's damage gathers in your body and banks up for later. Info here on choosing proper protection.