Performing the glitch
Shadow Temple Early can be performed in three different ways. The first method involves going to the elevator door directly in front of the loading zone and performing a clip to get through it. This clip is very special because it is one of the few uses of Frame-Perfect clipping in 007: Nightfire. A Frame-Perfect clip is very similar to a normal clip except you have to press the crouch button on a specific frame to clip through a wall. For the North American NTSC version, you have to press crouch two frames before Bond fully stands up after doing the clip motion. On the European PAL version, you have to press crouch one frame before Bond stands up. It's this difference in timing that makes this method of Shadow Temple Early much harder, if not, impossible on the North American NTSC version of the game. A video of This method can be found here.
The second method for Shadow Temple Early is to perform a Frame-Perfect clip on the elevator door on the right side instead of the one directly in front of the loading zone. Once you get out of bounds, navigate your way to the loading zone and press the action button to go to the next section. You do not have to be inside the elevator to activate the loading zone when you are out of bounds. This method is slightly slower but is confirmed to work on all versions of the game and a video of it can be seen here.
The third method for Shadow Temple Early is slightly slower than the other two but much easier to perform. Go to the elevator door on the left side and perform a clip to wedge yourself into the ground. Do not crouch again or you will fall completely through the floor. Now look toward the elevator door and cycle through your weapons or gadgets and crouch at the same time while moving forward. You should get through the elevator door this way. This method was discovered by Veman3000 on July 21, 2016 and a video of this method can be seen here.
History of the Trick
Shadow Temple Early was discovered by OllieNK on January 26, 2016 during a livestream on twitch.tv. A highlight from that stream can be seen here. This was the second use of Frame-Perfect Clipping discovered in 007: Nightfire. Shortly after, the community got together to understand the clip and find consistent ways to pull it off. For some reason, clipping through the left elevator door (as seen in the video linked before) appears to be impossible on the North American NTSC version. However, Lo1ts discovered a different setup that is confirmed to work on all versions. A few months later, Veman3000 found a different way to clip through the left elevator door that is slightly slower, but more consistent.