A loosehead prop lines up for the scrum on the left hand side of the hooker in the front-row, and the tigthead on the right hand side of the hooker. When the two front-rows interlock with each other for the scrum, the loosehead has one side of his head out of the scrum (the left side), and scrummages against the opposition tighthead. The tighthead has both sides of his head in the scrum, and scrummages against the loosehead.
Prop#1: Get your ass over here Carmen!
Prop#3:(to other prop)ohmigod when is she ever gunna get it?
The term originates from the basic inventory of the company being the "property" of the owner.
General use is to give authenticity to a performance by adding a prop to give the actor "business". Interacting with a brush, sitting at a dressing table in a scene sets up the "suspension of disbelief" along with sets and costuming.