There has been a lot of confusion regarding the 23 rule, especially when it is applied after a team has to double shoot a player. While it is explained in the "Official Team Manual" on page 33-34, below is a little different explanation from the National Tournament Rules.
No team may play five players whose combined skill levels exceed 23. In addition, a team must show it could have fielded a legal team (meaning it could have fielded 5 players that did not exceed 23) if the match had gone the entire 5 individual matches. If the total skill levels of the lowest five players listed on your roster is equal to or less than 23, then your team can meet the 23-Rule. This means a team may not lead off with three players whose skill levels add up to 19 unless there are two 2’s listed on the roster. A team may not try to win with its first three players and disregard the 23-Rule.
If the total skill levels of the lowest five players listed on the roster exceed 23, the team will have to play four players whose skill levels do not exceed 19 in the Open Division (16 in the Ladies Division) and forfeit the fifth match. If the skill levels of the lowest four players on the roster exceed 19, then they can play three players to 15 (13 in the Ladies Division) and forfeit the fourth and fifth matches.
Individual matches may be forfeited at anytime during a team match. If an individual match is forfeited after the rack has been broken in that match, the skill level of both players in the match will count towards the 23-Rule. If an individual match is forfeited before the rack has been broken in that match, the player on the team receiving the forfeit remains eligible to play again as the forfeit does not count as a match played. Both teams must be able to show at the end of the team match they could have fielded a legal team. Meaning they could have fielded five players that did not exceed 23 had all five individual matches been played.
For example, if the opposing team puts up a SL7, your team cannot forfeit using an unavailable player so your opponent can’t play their SL7. The opposing team would regain the use of their SL7 as long as they can show that they can still remain within the 23-Rule had all five individual matches been played.