A crop cutting device comprising: a crop guiding surface including a plurality of substantially parallel slots extending in a direction of travel of the crop over the guiding surface; a plurality of knives pivotally mounted below said guiding surface, wherein each knife is aligned with a respective slot and is pivotable about an axis extending substantially perpendicular to the slots between a retracted inoperative position in which it is located substantially below said guiding surface and an extended operative position, wherein at least a cutting edge of said knife projects above said guiding surface; a plurality of movable operating members, wherein each operating member is associated with a respective knife and is movable from a first position in which the knife is in its retracted inoperative position to a second position in which the knife is in its extended operative position, and wherein each operating member includes a spring loaded part which allows the knife to move to its retracted inoperative position while the operating member is in its second position; and a selector mechanism configured to selectively hold at least the spring loaded part of at least one operating member to maintain the corresponding knife in its retracted inoperative position while an operating member associated with another knife is moved to its second position; wherein the selector mechanism includes a rotatable shaft extending substantially perpendicular to the slots and carrying a plurality of cam elements (50A-F), wherein each cam element (50A-F) is arranged to be moved to a position for blocking a respective spring loaded part upon rotation of the shaft from a non-holding position to a holding position; and wherein the cam elements (50A-F) are substantially parallel; characterized in that each cam element (50A-F) is individually mounted on the shaft; and the shaft is axially movable between a locked position in which the cam elements (50A-F) are aligned with the spring loaded parts and an unlocked position in which the cam elements (50A-F) are offset with respect to the spring loaded parts and in which the shaft can rotate. a crop guiding surface including a plurality of substantially parallel slots extending in a direction of travel of the crop over the guiding surface; a plurality of knives pivotally mounted below said guiding surface, wherein each knife is aligned with a respective slot and is pivotable about an axis extending substantially perpendicular to the slots between a retracted inoperative position in which it is located substantially below said guiding surface and an extended operative position, wherein at least a cutting edge of said knife projects above said guiding surface; a plurality of movable operating members, wherein each operating member is associated with a respective knife and is movable from a first position in which the knife is in its retracted inoperative position to a second position in which the knife is in its extended operative position, and wherein each operating member includes a spring loaded part which allows the knife to move to its retracted inoperative position while the operating member is in its second position; and a selector mechanism configured to selectively hold at least the spring loaded part of at least one operating member to maintain the corresponding knife in its retracted inoperative position while an operating member associated with another knife is moved to its second position; wherein the selector mechanism includes a rotatable shaft extending substantially perpendicular to the slots and carrying a plurality of cam elements (50A-F), wherein each cam element (50A-F) is arranged to be moved to a position for blocking a respective spring loaded part upon rotation of the shaft from a non-holding position to a holding position; and wherein the cam elements (50A-F) are substantially parallel; characterized in that each cam element (50A-F) is individually mounted on the shaft; and the shaft is axially movable between a locked position in which the cam elements (50A-F) are aligned with the spring loaded parts and an unlocked position in which the cam elements (50A-F) are offset with respect to the spring loaded parts and in which the shaft can rotate.