This one is not so much a rule as a great help! When you sign on at a League event you’re given a chip, an arm number and a back number.
The chip system is terrific as it saves our volunteer team hours each weekend writing up names and times etc. However, we still keep a manual back up of the race … just in case! The line judges/lap recorders rely on “well pinned” numbers to make that record.
Think about your position on the bike … when you’re forward on the bars you don’t want extra strain on your jersey.
Not too far around the front of the arm or the judges won’t be able to see it. Remember you are approaching them in a bunch at incredible speed.
Please use four pins, one in each corner. That’s 4. Not 2.
Arm numbers are just as important as back numbers and vital when the back number is covered in mud!
Again, think of your position on the bike … the number needs to be comfortable when you’re forward on the bars, and not so tight that it pops the pins or tears your jersey.
Pin low down so that the number is easily visible – not obscured by your flowing hair, a hood, etc.
Use four pins, one in each corner. Some add extra pins each side for extra security.
You can keep your numbers after the event, but don’t forget to return your chip.
(adapted from Mary’s original at https://www.ndcxl.org.uk/2013/11/12/rulebook-101-number-pinning/ )