How to properly layout this frame?

Mizmas

I'm messing around with frames, and i want to try an implement a side menu, but why doesn't the red frame properly connect with the header and the footer when the layout margins are all set to 0?

Ui file download

Pl45m4

@Mizmas

Try

body->setFrameStyle(QFrame::NoFrame);
footer->setFrameStyle(QFrame::NoFrame);
header->setFrameStyle(QFrame::NoFrame);
side_menu->setFrameStyle(QFrame::NoFrame);

Mizmas

@Pl45m4 Thanks it worked, never had this problem before. It can be set in the designer too