Grip.
Understanding.
That which is accessible; that which is within one's reach or ability.
To take advantage of something, to seize, to jump at a chance.
To grip; to take hold, particularly with the hand.
To understand.
A pin in the form of a clasp, which has a guard to cover the sharp point; used to join two pieces of fabric, etc., together temporarily.
The pin of a hand grenade, which prevents accidental detonation.