Jim,
By "extra knob", do you mean the 1" ball adapter with a flat plate on one side. If so, this is a iFly to RAM adapter. Simply insert the flat side with the metal plate into the key-hole slot on the back of the iFly, slide it to the narrow end of the slot and give the ball about a 1/4-12 turn clockwise. No tools needed. This will tighten the ball on the back of the iFly so you can then mount into the RAM arm coming from the base. The wing nut on the arm will secure both ends once you have your desired position. I hope this helps.