Our RadMaskedEditBox supports four different mask types. They are None, Numeric, DateTime and Standard. For each of these mask types there are different characters that define the type of input.
For example for the Standard mask type the "L", "a" ,"#" and "\" characters have special meanings. For additional information please have a look at our online help which you can find here
Do not hesitate to write back if you need further assistance.
the Telerik team