2 Toilet Venting Diagram

Can someone tell me where I can see a venting diagram for 2 toilets sharing a wall so that I can guess at the fact the vent is still clogged where I could not snake from the roof. Say just before the two toilets that there might be a clog the snake effort from the roof just could not make the corner and the clog maybe is still partial and must be done at ground level toward the 2 toilets. Thank you.