a stapler and related method for use to bind documents are disclosed in which a selective one of a plurality of different size staples all stored within the stapler itself may be selected for dispensing without necessitating the removal of any staples of a non - selected size from the stapler , or reloading the stapler with the selected size of staples . the stapler contains a magazine having a plurality of cassettes into which staples of different sizes are loaded , with the cassettes being located one atop the other in a stacked array of rows of staples . a selector mechanism is used to alternately , selectively allow one of the rows of staples to be fully advanced to the end of the stapler from which the staples are dispensed , with the other rows of staples being actively urged back away from the end of the stapler from which the staples are dispensed to allow a staple from the selected row to be dispensed .