From 
Keep rug from slipping If you have a throw rug that tends to skate across the floor, keep it in place by sewing a rubber jar ring or two on the underside in each corner.
Play indoor quoits What else can you do to keep antsy pre-schoolers happily occupied on a rainy day? Turn a stool or small table upside down and let them try to toss rubber jar rings over the legs.
Protect tabletops Protect your tabletops from scratches and watermarks by placing a rubber jar ring under vases and lamps.