stock grid is a type of obstacle used to prevent livestock, such as sheep, cattle, goats, pigs or horses from passing along a road which penetrates the fencing surrounding an enclosed piece of land. It consists of a depression in the road covered by a transverse grid of bars or tubes, normally made of metal and firmly fixed to the ground on either side of the depression, such that the gaps between them are wide enough for animals' legs to pass through, but sufficiently narrow not to impede a wheeled vehicle or human foot. This provides an effective barrier to animals without impeding wheeled vehicles, as the animals are reluctant to set foot on the grates.