Patent ID: 7837422

Claim:
A method of binding a sheet stack having a mounting hole by a binder unit which comprises an elongated binding body and two fastening arms extended from said binding body, comprising the steps of: (a) slidably inserting said two fastening arms into said mounting hole of said sheet stack at a top side thereof until a first binding portion of said binding body is biased against said top side of said sheet stack at an edge portion thereof; (b) adjustably bending a second binding portion of said binding body to bias against a bottom side of said sheet stack at said edge portion thereof, wherein said binding body is adjustably bent in a U-shaped structure with respect to a thickness of said sheet stack; (c) aligning an elongated guiding slot of said binding body with said mounting hole at said bottom side of said sheet stack when said second binding portion of said binding body is bent to said bottom side of said sheet stack, wherein said guiding slot is longitudinally extended along said second binding portion; and (d) detachably engaging said fastening arms with said second binding portion of said binding body, wherein said fastening arms are bent for resting on said bottom side of said sheet stack to reinforce said edge portion of said sheet stack being securely sandwiched between said first and second binding portions of said binding body.