Trinity Knot Used in Ironwork or Stone Crosses
Puzzle 18 of At the Ballet Hard Pack
Question is: Trinity Knot Used in Ironwork or Stone Crosses
and the answer is: TRIQUETRA
Word Meaning:
TRIQUETRA — A shape formed of three vesicae piscium, sometimes with an additional circle, a symbol of things and persons that are threefold (including the Christian Trinity), and a symbol of protection in Wicca.
Definitions from Wiktionary.