Bine hooks run along the main feed chain about every 3.5 m or 12'. There are typically 7 hooks in total. Made of cast iron, they can (and do) shatter under excess force. An extra bine hook or two should be on hand for every harvest. Having one missing bine hook can reduce your picking rate by 14% or more. That's an extra 1 hour and 20 minutes of picking per 10 hour harvest day if one breaks.