Earning Checks on the Player's Turn

I’ve done some preliminary searching around, so please let me know if I’m treading on worn out territory here, but I can’t find anything explicit in the rules about whether or not player’s should be allowed to use their traits to earn checks on rolls being made in the player’s turn.

I understand that you can’t use more than one method to earn checks on a single roll, and it’s assumed that players are using these rules in the GM’s turn, but it’s unclear.

Help, anyone?

You’re looking for “Traits and Checks in the Players’ Turn” on p. 75: players can earn checks only in the GM’s Turn.

Thank you.