the toothbar in this way the teeth 62 associated with the toothbar may be swung away from the cutterbar 44 to provide access for service to the toothbar for the purpose of keeping the latch pin 100 in its retracted or release position when the pin is misaligned with the hole 80 of the outer arm section 72 the outer arm section includes an arcuate portion 110 fig2 and 5 having an outer dimension located at a radius from the mounting pin 84 which is equal to the distance the release pin 100 is from the pin 84 so that bottom of the release pin cup 104 remains in engagement with the arm section portion 110 throughout the range of pivotal motion of the inner arm section 70 relative to the outer arm section 72 it is here noted that once repairs or other service is finished the operation of the reel may be resumed with the result that the released pin 100 will be automatically returned to its extended latch position once the outer arm hole 80 again becomes aligned with the pin cup 104 the operation of the invention is briefly stated as follows assuming the mower conditioner 10 to be under tow by a prime mover such as a tractor in normal operation mowing and windrowing a crop a drive coupling to the prime mover will be engaged for causing reciprocation of the sickle of the cutterbar 44 and for causing rotation of the reel 50 the toothbar guide arm 64 will be in its normal operating condition wherein the latch pins 100 are received in the holes 80 provided in the outer arm sections 72 so that the inner and outer arm sections 70 and 72 move in.