Abstract: A harvester thresher has a cutting mechanism, a reel having reel supporting arms, an exchangeable attachment which is releasably connected with the cutting mechanism, sliding shoes in which the reel is rotatably supported and which are synchronously forwardly and rearwardly displaceable on the reel supporting arms for adjusting the reel relative to the cutting mechanism, shaped parts arranged on the cutting mechanism and the attachment for moving the cutting mechanism and the attachment to a proper position, driving and pulling elements arranged on the sliding shoes and on the attachment and connectable with one another at a predetermined distance between the cutting mechanism and the attachment so that by moving back the reel the attachment is movable to an end position.