Hang on a little bit and we'll tell you about the chip's purpose. You'll need safety pins. Boxes of loose pins are available at number pick up. Take four to six pins. Use four to attach your race number and one to attach your baggage tag.
Some runners are thrifty, environmentally conscious and reuse safety pins.
Be sure to remove the pins from your clothing after the race. Don't just toss the shirt, number and pins into the laundry for extraction later or you'll likely end up with tiny rust spots at the pinholes. Pin the race number on your front. It must be visible for race officials. Do not fold, cut, write on or otherwise deface the tag.