i was wondering if i added a clip around one of my models if the zombies would be able to mantle the object and get into the playble area to get the player?

If you add a traverse they don't even need a clip. It depends what you are using it for. If its just a random static model in your map I would clip it. If its something the players/zombies can't reach I wouldn't bother with clipping. If you want the zombie to mantle though you will have to use the wall_hop traverse just like when you are making a window(but with no window this time(unless you want one)).

ok so the spot i want the zombies to mantle i dont want the players to be able to jump over it but i want the zombies to be able to

ok so the spot i want the zombies to mantle i dont want the players to be able to jump over it but i want the zombies to be able to

Then add a player clip.