Any dunnage used with palletised (or other unit) loads should be limited, and lengths kept to prevent obstructing or fouling mechanical equipment, cargo in the stow, and handling operations. Sometimes it is necessary to place sheets of plywood, chipboard or fibreboard on edge in the stow to prevent the cargo on one pallet "locking" with the and so the unloading operation. It is important when operating below decks with mechanical handling equipment that the decks are free of obstruction: loose dunnage, rubbish, etc.