Deinterlace footage?

Sometimes I'm given interlaced footage to mix with progressive footage. My projects are always progressive.
What I've been doing is right click interlaced clips in their bins. Choose “Clip Attributes” and check “Enable Deinterlacing”. This seems to deinterlace the clips as seen in my viewer.
However in the Project settings/Master setting/Playback frame rate has an "Enable field processing" check box. I don't have this checked but the interlaced field lines do disappear in when played back in the Timeline.

So, when/why would I check the box in Project settings?

It's late and I could be a little tired, but if I remember it's for interlaced project and/or to render interlaced files.
But it's late and I could be a little tired.

Ugo has it right. That project setting is for Interlaced projects, which you don't have.

The deinterlacing in DR is not top notch. If you have the time and want the quality, try QTGMC.

Ugo has it right. That project setting is for Interlaced projects, which you don't have.

The setting processes each field separately when using interlaced source media. It also works in conjunction with the Field Rendering option on the Deliver Page when you need to deliver an interlaced master format.