Today's rule has two parts to it. The easier part to explain is that each skater's number must have at least one numerical digit. If a skater wants to use "HERO" as their number, they would have to use "H3RO", "HER0", or a combination of the two. At least one numerical digit keeps it a number (at least that's what I tell myself). I really don't know why skater numbers must have a numerical digit, but they must.

The other part to this rule is that characters in a skater number must be alphanumeric, with no symbols. For those who like to stretch the bounds of rules, alphanumeric means 0-9, a-z, and A-Z. Wikipedia has a great article on alphanumeric.

http://en.wikipedia.org/wiki/Alphanumeric

This was done because there used to be all kinds of ridiculous numbers in roller derby. I used to peruse Twoevils and laugh. One time I swear I saw the number "&1&2&3&4&5&6". Can you imagine a referee trying to call a penalty on her during a bout? Let alone, how would she fit that on her arm? And that brings up the mention of symbols. If a character is not alphanumeric then it is a symbol. Since alphanumeric includes Latin letters and Arabic digits, letters and numbers from other languages or alphabets are allowed. Yes, lambda is a letter, but it is Greek and therefore not considered alphanumeric. The infinity symbol is just that, a symbol. Same with the at symbol.

So to sum up, skater numbers may be four characters maximum (if that is news to you, see yesterday's rule), made of alphanumeric characters only, and one of them must be a numerical digit.

https://www.facebook.com/RollerDerbyRuleoftheDay/posts/276705035701693