Barrier Tag

These tags are special pieces of paper inscribed with the kanji to, which is short for the word. The tag most likely forms a barrier to protect whatever is located within the perimeter it forms. When these tags were used, shinobi were stationed above them which indicates that the technique might require maintaining.

Trivia

 * There were most likely several other tags and shinobi stationed around the area so as to complete the barrier's formation.

Reference
Sello Barrera