Before backing the tractor under a trailer during coupling, what should the position of the trailer be?

TRAILER HEIGHT FOR COUPLING: Before backing under, the trailer should be at the correct height — low enough that the trailer nose will be raised slightly (about 1/2 inch) when the tractor's fifth wheel contacts and backs under it; if too LOW, the tractor may strike and damage the trailer nose or hit the landing gear; if too HIGH, the kingpin may not enter the fifth wheel jaws properly (may slide over the top — a dangerous incomplete coupling); CHECK alignment of the kingpin with the center of the fifth wheel; back slowly, using the fifth wheel to lift the trailer slightly; this ensures the kingpin seats properly into the locked jaws; proper trailer height is a key pre-coupling step — getting it wrong causes equipment damage or a dangerous high-hitch (where the trailer rests on top of the fifth wheel rather than locked in); always verify height before backing.