Frost nail

a nail with a sharp head driven into a horse's shoe to keep him from slipping.
- Knight.

See also: Frost

References in periodicals archive ?
C Frost Nail Lacquer in Beiged Bliss Slightly insipid colour needs at least two coats.
On mornings like these, a knock would come at the door or even at the window for George to put frost nails in the horses' shoes to stop them slipping.
Some gardeners say the flavor isn't as good as nondeterminate tomatoes, which grow on vines and produce all summer long, right up until the first frost nails them.