A draper header has a transverse main frame supporting center, left side and right side belt conveyors and including a plurality of transversely spaced knife support members that extend forwardly beneath the belt conveyors from right and left lower rear main frame members and have forward ends on which a transversely extending knife is supported. Each belt conveyor includes a frame disposed within an endless belt and having a rear side hinged to a respective lower rear main frame member for pivoting upwardly between operating and belt-changing positions. Brackets are removably fixed across the length of the knife and have rear edges extending above front edges of the belts when the conveyors are in their operating positions. At least one height adjuster is mounted between the main frame and each conveyor frame for moving each conveyor to its belt-changing position once the associated brackets are removed from the knife.