Bib numbers let race administrators distinguish between thousands of runners and ease the seemingly impossible chore of collecting a time for each and every one of them. The first thing to know about bib numbers is that they are usually assigned at check-in, when participants fill out a form indicating their preferred number and any special requests (such as allergic to latex). The second thing to know about bib numbers is that they have no practical use after races start. They are used only to identify runners so that prizes can be given out accurately. Race directors may also use them to record results or include volunteers in awards ceremonies. A third thing to know about bib numbers is that they are usually printed on both the front and back of the singletrackly branded shirt worn by participants. In multi-stage races, numbers are often also included on bags, jackets, and other items used by the racers. A fourth thing to know about bib numbers is that they can be any sequence of numbers between 1 and some maximum value. These ranges are typically started from 0000 and increased by one for each winner of a prize. There is no rule against using numbers in other sequences, such as 0123 or 987654321.