when to stretch

i have a question of when to stretch. partially erect, fully erect, etc? i watched the video for stretching and it seems like they are fully erect i cant really tell but from some of teh stuff i read it seems like you are not suppose to stretch when fully erect

thanks for your help

Certainly you have to stretch only in flaccid state not in partially or fully erect
and usually before jelqing.

cos