[Groop]Once again, what is that blue buckle called?

[Jeff Allen]

I've been lurking on the Groo list for right near 5 years now and I
think this question comes up once a year.  So to keep the annual event
going , here goes...

What is the blue buckle that is on Groo's sling called?  I remember Mark
stated that Sergio told him once, but Mark forgot what Sergio said. 
Does anyone know the name of this thing?

While we're at it.  Does any one have any theories on how the buckle
works?  Other than the knots tied around the top and bottom of the
buckle to keep it from sliding?

Confused and tormented,

Jeff