I’ve taken part in a couple of races recently and didn’t want to risk making holes in my top by fixing my race number to it with safety pins.
Fortunately, I had a Spi-Belt that I was going to wear anyway so I folded the number over, stuck the 2 ends together and looped the belt through it. Most race numbers have a bit of excess paper at the top and the bottom which is perfect for doing this whilst still leaving the number visible.
Here are some photos below to show what I mean…
You can see how the number is still clearly visible from this photo, and no holes in my running top…