A lot of people have asked me that very question, especially when they get their first BOHROK, so here’s your answer. It holds rubber-bands prior to assembly. That’s it. LEGO® apparently decided it would be cute to turn it into a usable part, but I have yet to hear of a set that actually includes these in the assembly.

Anyways, the above pic shows a small piece from the four smaller RAHI on the left, the same small piece from the BOHROK on the right, and the large piece from the MANAS set in the center.