Is there metal in the manufacturing of cabinets?

I went to add hardware (knobs) to my kitchen cabinets. As I was drilling I hit metal. Do Cabinet makers use metal for the manufacturing process? How do I know where the metal is so I can drill around it?

Public Comments

1. I could be wrong, but I don't believe there is metal in the cabinet. http://www.wood-mode.com/main_sections_about_wood-mode/About_WM_Introduction.htm
2. Metal fasteners are sometimes used in the corners of cabinet doors. Usually you can see the on the back side. Move your knob hole up or down an inch.