what is grip unknown?

[Jacob Schmude <jacobs surferie net>]

Hi all
Occasionally in some applications, I'll come across an unknown control with 
the field lable "grip." On my braille display, it shows:
UNK Grip
and when speaking, it says:
grip unknown
This happens most often in balsa, but I've seen it in a few others. Does 
anyone know what this is supposed to be? I can't do anything with it, it 
just seems to be there.