truck drivers i gotta question

so i was on youtube yesterday looking at some peterbilts and i noticed some of them are hella low and long. how are people doing this

Some of them are done by putting a day cab on the frame that came with a sleeper. Others are just complete custom frame extensions. I had a freightliner custom sleeper and it was like 8 feet longer than a regular. As for lowering them they make a drop shackle like those for a pickup.