盖子可以被吹开（一边固定），防雨，鸟。。。

screen is used sometimes in addition to cap. I have seen connections to roof and side of house. 

所有跟帖： 

• 可是我从attic里面捅了捅那个到房顶的盖子，为什么不动呢？不懂的话，脏东西出得去吗？ -最爱荷花- ♀ (0 bytes) () 08/02/2023 postreply 07:05:13

• 看看有没有vertical opening？if not, could the top cap be stuck? -RomaVacation- ♂ (29 bytes) () 08/02/2023 postreply 08:29:47