In general, the grip of a fastener is the thickness of material or parts which the fastener is designed to secure when assembled.

To seize or hold fast. That portion of a rivet between the two heads after being driven. The thickness of material through which pins, bolts, or rivets penetrate.

to grip or seize, as in a wrestling match; "the two men grappled with each other for several minutes"

The actual thickness of the panel or stack up of panel into which the insert is installed. All performance testing of blind threaded inserts should report the grip used, as it can have a significant effect on performance

The thickness of the assembled materials or parts for which the fastener was designed to secure.

The thickness of all materials that a bolt is designed to secure.

The nominal total panel thickness for which a fastener is to be used. (This is usually customer defined).