Forum:KB:Checkpoint problem

Hey everyone, i hope someone will be able to help me : actually, when the skywalker group ( leia/han , luke/mara i think and maybe more people ) need to get past a checkpoint, they do it by passing for their imitations , and i'm getting crazy 'cause i can't remember in whick book it is and it has been two weeks , if anyone could help me or at least help me narrow my search xD.