Solved TWM video fullscreen

When I watch online videos I want to fullscreen the video,but it has a border when I fullscreen.How to remove the border?
Within TWM, which media player are you using? Then look up the man for that media player and it will tell you.
I mean online videos, not videos played in the video player. I watch videos fullscreen without problem within Xfce and other DEs.Within TWM, there's always a title bar showing on top of applications. I don't want that title bar.
An application communicates with the window manager. One thing an application can ask is "full screen, without window decorations". But: All of this is a) optional, and b) in this case part of the "extended window manager hints", which are - afaik - unsupported by TWM.