Then the canny thief arranges for a few of these to be given to the local constables and city guardsmen, ornamented in such a fashion as to pay homage to the order of law keepers. Then at night, the thief slips on his ring, rendering the guardsmen invisible to him, and him, invisible to them. (this would have to be a modified set, otherwise everyone would notice when the guards suddenly couldnt see each other)
Often when a classroom is full of unruly students, it can become difficult for a teacher to maintain order while teaching an effective lecture. In cases like these, instructors often require each student to wear a Ring of Mutual Exclusion during the class period. This makes each student feel like he or she is the only student in a large, empty classroom. The instructor usually finds this a much easier environment to teach in. The professor will occasionally slip on a ring for a second just to see if any of the students aren't wearing theirs.
Some of the more eccentric thrill seekers will arrange for as many as a dozen gladiators to fight to the death in a small arena while each is wearing a Ring of Mutual Exclusion. Each combatant is unable to see his opponents or even feel them until, by randomly swinging his sword, he finally draws blood. An archer is usually hired to wear a ring and oversee the combat. If a contender should remove his ring, he would instantly become veiwable by the archer and subsequently shot until he died. Such tournaments often attract a large bidding competition.
Easter Egg Hunt:
During a race or scavenger hunt, the overseer will often require the competitors to wear Rings of Mutual Exclusion to provide a little more viewing pleasure. Racers will often run into each other and fall to the ground without feeling the collision. The resulting humor is often very gratifying. In a scavenger hunt, one seeker could be reaching for an item only to have it disappear in front of his eyes when another seeker grabs it first.
Clever judges use Rings of Mutual Exclusion to allow all of the witnesses and suspected felons into the same room without them hearing each other. A guilty criminal usually becomes very nervous when the judge asks a potentially convicting question and the answer given is completely unheard. The guilty often break down and confess when witnesses don't have anything useful to say. The tension it creates is a very useful tool.
A patient thief looks for someone who owns a Ring of Mutual Exclusion. When she sees someone wearing a silver ring, she will slip on her own ring for a moment to see if the target disappears. Once she knows that someone owns a ring, she just has to wait outside his house while wearing her ring until she can't hear or see the target. She can then steal all she wants at her leisure, but if she takes too long, the target may notice items disappearing into thin air.