A book of rules that has not yet been written, but is put into context by what is understood to be RULE! Ones intuition, gut feeling or standards. Simply put; morals.
Dude you never get your head where you make your bread. Rule 345 in the unwritten book of the road...
She should have never slept with her best friends man, it's in the unwritten books of the road.
When you are nailing a seasoned veteran woman from behind, aka doggie style (look up if needed), and she is on all fours... in mid-thrust you grab or kick arms where her head falls to the ground and her forehead get a carpet or floor burn.
Having inorganic material (ie dirt, small gravel, sand, etc.) enter and irritate the vagina. Can show in forms of itching, pain, bumps, and possibly bleeding. Most common irritant is sand.