One simple question about RF circuit

In some schematice for Rf circuits,

there is some strange flag, as shown in the attached schematics.
(PDF format)

I think it should be:
1) Bypass cap,

2) Parasitic Cap in PCB and PAD lead.


I never meet this kind of schematice.

Thanks a lot.

This is feedthrugh capacitor. It's purpous is to effectively block or filter RF to escape metal enclosure. In simplest form it is only capacitor and can be made as a PI or T filter.
Atached is a picture of one of the types of feedthrough capacitor.

I appreciate your kindly help.

I also found some detailed materials for it.

The short version: it is sort of a decoupling capacitor.