Just tricks. The corner is an angled steel piece, not a hinge. The corner still needs the trimwork to cover that. Just ran out of oak.

Oh, that's not the left speaker. The left is behind the surround. Just kidding. Actually I've never had any issues with the speaker there that I know of and have never been concerned. Thanks for bringing up something to worry about. The powered subwoofer built in isn't actually used in that speaker and it's been that way for 8+ years so I'm not going to worry about it