The KO on the back ... yes, I suppose you could connect your Romex directly to the plugmold. Silly me, I've always been starting off from either a Wiremold box or an EMT transition piece.

I was trying to imagine how to connect plugmold to a wall box directly, without a Wiremold box jutting out of the wall.

I guess what I'm trying to imagine is a new product ... plugmold with outer flanges, for setting flush into walls. I was trying to imagine how that product would, in turn, mount to a 4-square box.

Today's project was to move my computer desk into another room. As you might guess, this meant hanging two lengths of corded plugmold. All I can say is .... the Wiremold brand is a lot nicer that the other stuff! Easier to mount, neater package, etc.