THE SAFETY HARNESS
Coming in a variety of styles and colors, the safety harness can save you from injury or, in extreme cases, death. Though it may save you from a gruesome fate, a harness will not save you from public ridicule. Just as carrying a partial bundle of shingles can make you look like a sissy, wearing a safety harness can make even a strong man appear effete.
My recommendation for precisely when to wear a harness depends on the height and slope of a roof. Only a trapeze artist would laugh at a man for wearing a harness on a three-story building. For lower roofs, you might try camouflaging your harness by wearing clothes over it. However, this has the dual disadvantage of chafing the legs and making some very peculiar bulges in your pants.
A safety harness can be expensive to rent or buy. Leave it to me to find a cheap substitute. Try tying a rope around your waist. Using a double square knot, secure it to a rafter. This will give the PSYCHOLOGICAL benefits of the harness at a fraction of the cost of a real one.
Unfortunately, a rope around the waist has a minor drawback. It seems the rope's lead line has potential for getting tangled in your feet. Coupled with tearing felt paper and the very nature of unsecured shingles, this can lead to the unpleasant sport known as shingle surfing.