What is a 2-pop? Also known as a "2-beep", it consists of a visual flash (1 frame in length, full screen white preferred) and matching audio beep, 1 frame length, on ALL audio tracks, placed exactly 2 seconds before the "first frame of action", abbreviated as FFOA. The FFOA is where your program begins. The FFOA is not necessarily the first visible image since many films begin with a fade up from black. The 2-pop is how we know exactly where the film begins! An acceptable alternative to a 2-pop is a countdown sequence such as an "academy leader", where "the two" is placed exactly 2 seconds before first frame of picture. If you do not know what a "countdown sequence" is, you are not ready for me!
The 2-pop is often placed at 59:58:00 with the FFOA at 1:00:00:00, but this is by no means a standard.
A similar flash-beep is often placed at the end of the film. It helps us verify that there have been no speed problems or dropped picture frames. While the term "2-pop" is meant to denote only the one at the beginning, I think it is okay to use the term for both of them.