Sam,
If you go to our Parts Manuals section, scroll down to the Kohler powered 200/400 tractors and open that link. The A1278 parts book incorporates PIN 9692238, which is your tractor. It's the seventh icon down from the top.
Then go to the Operator's Manual section and scroll down to the Kohler powered 200/400 tractors once again and open that link. Scroll down and find manual 9-4392 or 9-4393. Both are for your tractor. One is just a slightly new version.
Most likely, the metal bar is part number C18147 and is depicted in the drawing on page 42 of the manual as Item 22. This sawtooth bar gets pushed downward by the operator after he fully depresses the brake pedal. The bar is held down as the operator slowly lifts his foot off the brake pedal, allowing the teeth on the bar to engage the dash tower and that keeps the parking brake engaged. To release the brake, the operate simply depresses the brake pedal again and the sawtooth bar will flip up, out of the way. All too often, owners fail to adjust the parking brake band and the lever slips behind the dash tower and bends.
This problem can usually be rectified by removing the bar and carefully straightening it. As long as it is not cracked, then it should be fine.