Shen ring

In ancient Egypt, a shen ring was a circle with a line tangent to it, represented in hieroglyphs as a stylised loop of a rope, bound to a stick. The tool used by builders and architects. Shen Rings can most often be seen in the clutches of Horus The word shen itself means "encircling" in ancient Egyptian, while the shen ring itself represents eternal protection. What the French called a cartouche is in fact a elongated Shen Ring encircling a name of a Pharaoh or God/Goddess, thus ‘eternally protecting’ that personage.

In Gardiner's sign list, it is sign V9.

shen šn in hieroglyphs
Gardiner: V9