[OutsiderFan]

At what point specifically do these guys earn a letter?

Typically these designations are used to define college football experience:

HS:  Has yet to participate in a season on campus
RS: Player is coming off red shirt year
JC:  Junior College player who has not participated in a season on campus
L (1L, 2L, 3L): Years the player has lettered; played in at least one game (a player may letter four years, but is never shown on the roster as 4L, because after they receive a 4th letter, they are off the team)
SQ: A player who has never seen any game action

Players earn a letter each season they have played in at least one game and not redshirted. For example, Ty Montgomery lettered his Frosh year and would be "1L." Wayne Lyons didn't.  Though Lyons played, he didn't play enough to use up a year of eligibility.  Since you can't letter in a year you did not officially play, Lyons did not letter in 2011 and is a RS.

[OutsiderFan]

At what point specifically do these guys earn a letter?

Typically these designations are used to define college football experience:

HS:  Has yet to participate in a season on campus
RS: Player is coming off red shirt year
JC:  Junior College player who has not participated in a season on campus
L (1L, 2L, 3L): Years the player has lettered; played in at least one game (a player may letter four years, but is never shown on the roster as 4L, because after they receive a 4th letter, they are off the team)
SQ: A player who has never seen any game action

Players earn a letter each season they have played in at least one game and not redshirted. For example, Ty Montgomery lettered his Frosh year and would be "1L." Wayne Lyons didn't.  Though Lyons played, he didn't play enough to use up a year of eligibility.  Since you can't letter in a year you did not officially play, Lyons did not letter in 2011 and is a RS.