A flexible sheet member having a first dust excluding packing and a first
auxiliary piece is tackedly held by an exfoliating sheet by an adhering
layer 8 at a back face thereof. When the first dust excluding packing is
exfoliated from the exfoliating sheet, and the first auxiliary piece is
exfoliated from the exfoliating sheet by following the first dust
excluding packing 6. The first auxiliary piece is formed with a cut line.
After pasting the first dust excluding packing to a cabinet, the first
auxiliary piece is separated from the first dust excluding packing.