Open the suitcase as wide as possible and balance the open suitcase bottom on a flat surface.
Measure across the open portion of one side of the suitcase with the ruler and add 1 inch. Cut four strips of ribbon to the measurement.
Attach the ribbon strips to the suitcase edges using the glue gun, pulling the ribbon strips taut and evenly spacing the strips to accommodate the height of the earring cards. Repeat the last two steps on the opposite open edge of the suitcase.
Attach additional ribbon to the edge of the suitcase opening with the hot glue gun.
Attach the earring cards to the ribbon by hanging the earring backs over the ribbon.