Timing straps have become essential to the modern-day triathlon. If final times and placing relied on numbers strung along a wire, the room for error would greatly increase. It's a good system to have as a backup, but electronic timing systems tend to be more exact and less prone to human error. In order for these to work, every athlete competing needs to have a timing chip secured to them throughout the race.
For this purpose, timing straps are a staple to modern triathlon racing. Made out of slim, stretchy pieces of fabric, they fit and stay securely around the ankle with a velcro strap. Wearable under wetsuits, having a reliable timing chip strap leaves you with less to worry about during the race.