Sherwood's pictures are related to pre-1977 911 cars that have non-vacuum boosted brakes. '77-up cars have a rod in the pedal assembly that leads up to the trunk where the master cylinder is mounted to the big round black vacuum booster. That booster is connected to the pedal rod via the large aluminum base that is bolted to the trunk floor.
To get access to the pedal rod, you must remove the carpet behind the pedals and then remove the floorboard behind the pedals. You can't get the carpet off the floorboard until you release the throttle pedal. Pull back on the throttle pedal to release the ball-socket rod that pops into the back of the pedal. To remove the floorboard, peel the rubber pads off the brake and clutch pedal. Once you have the pads removed and the nut at the bottom of the board, lift out the floorboard by wrestling it over the pedals. You have to fart around with the clutch and brake pedal positions a little bit to get the board holes past the pedals.
Once you have the floorboard removed, you will be able to see the brake pedal rod. It's #1 in the picture below. To adjust the length of the brake rod, loosen the nuts #4 and #5 that are adjacent to the upper clevis and lower spherical rod end. Note that the nut for the upper clevis is left hand threads. That means it ain't lefty loosey to loosen it! The reason the clevis end of the rod is left hand/reverse threads is to allow the rod to properly change length at both ends by rotating it.
Once you have the rod to the length you want it, cinch the jam nuts tight again and you're done.
