Pylons

The NCAA, in 1972, set the number to be used and in 1975 their use became mandatory.
Rule 1-2-6 states:

Soft, flexible four-sided pylons 4 inches by 4 inches with an overall height of 18 inches, which may include a 2-inch space between the bottom of the pylon and the ground, are required. They shall be red or orange in color and placed at the inside corners of the eight intersections of the sidelines with the goal lines and end lines. The pylons marking the intersections of the end lines and inbounds lines extended shall be placed three feet off the end lines.

Pylons on the end lines offer a visual reference for receivers. The two marking the inbound lines or "hash marks" are there as a reference for spotting the ball. Some would say they are not necessary, but not all fields are new artificial turf surfaces with nice white painted inbounds lines. For years the inbounds pylons were on the end line but were moved 3 feet back because receivers were knocking them while running routes in the end zone.
The two pylons on the goal line are critical to the game. They are placed at the intersection of the goal lines extended and the sideline, not only assist in making out of bounds calls, but also help in determining whether a touchback has occurred, and most importantly, whether a touchdown has been scored.

The goal line pylons sit on the sideline, and as such, they are entirely out of bounds. The end zone is entirely inbounds. Therefore, they are out of bounds behind the goal line.



The flank official should have been at the goal line to better make the call