Many scholars believe the sign is a knot formed of a flexible material such as cloth or reeds,[1] as early versions of the sign show the lower bar of the ankh as two separate lengths of flexible material that seem to correspond to the two ends of the knot.[2] These early versions bear a resemblance to the tyet symbol, a sign that represented the concept of "protection". For these reasons, the Egyptologists Heinrich Schäfer and Henry Fischer thought the two signs had a common origin,[11] and they regarded the ankh as a knot that was used as an amulet rather than for any practical purpose.[10][12]