Pitwalking in LA/DX can only be used to cross one-pit gaps downwards. Pitwalking specifically refers to this act without the use of menu buffering, otherwise it is called pit clipping. Pitwalking is very rarely used as it only works 1/8th of the time when done perfectly. Likewise, there is only one place where it is known to be useful
Line Link up like so (only his horizontal position matters):
Then, hold down. If you pressed down on one of the two frames that it works, he will clear the gap entirely, skipping a small section on the way to D1.