Antler crossbow nut and iron arrow heads from Buiston crannog, Ayrshire, c. AD 550 - 700.
The antler object is part of the trigger mechanism of a crossbow. The string was held tight by the upper notch, with the arrow resting against it. A trigger in the lower notch was removed, allowing the whole thing to turn, releasing the string and firing the arrow. Iron heads from arrows were also found on the site. It would be used for hunting.