Between Doorknob and Glass

• 1). See if there is a gap between the metal of the doorknob and the glass door.
  
  
• 2). Slide two fingernails along the bottom edge of the business card to crush the edges a bit.
  
  
• 3). Place the card in the gap between the doorknob and glass door.
  
  

Rubber-Band Door Hanger

• 1). Keep a few rubber bands in the briefcase, along with business cards that have a hole punched in one end.
  
  
• 2). Slide the rubber band through the hole. Turn it back on itself through the loop of the band and over the card. That makes a hanger.
  
  
• 3). Slide the hanger over the door handle.
  
  

Sticky

• 1). Stick the business card to the glass door with a glue stick.
  
  
• 2). Attach it with a bit of transparent tape.
  
  
• 3). Use the sticky side of a Post-it Note to stick the card to the glass. Write a brief note on the Post-it, such as: "Sorry I missed you."