As the temperature of a cooking hearth could only be manipulated by the size of the fire, a trammel such as this was an essential means for regulating the heat exposure to various pots and kettles. The chain would have been looped over an iron bracket or pole built into the masonry, allowing the links of the chain to hang below. The bottom hook would be used on the handle of the various cookware put before the flames. The smaller hook would act to fit itself on one of the various forged iron rings, thus adjusting the size of the trammel and the distance the various kettle/pot would be from the flame; allowing for better temperature regulation.
This exceptionally long example is particularly fine with two different types of hook on one end, enabling it to handle anything from a pot to a kettle to a cauldron, and the ring hook at the other. It would, without a doubt, have belonged to a very major establishment.