in such a way that a parallel shed or a v shed can be formed as is shown in fig5 the guiding rods 27 are respectively provided with a bush 40 and are disposed on the fixed shaft 5 so as to be spaced from each other by a spacer sleeve 41 as well as being secured against sideways displacement by disks or washers 42 a bearing bush 43 is provided between the bush 23 and the guiding device 27 which bearing bush keeps at the same time the webs 22 so as to be spaced from each other the bush 23 has a flank 44 at one end and an internal thread into which a bolt 45 is screwed in this bolt 45 fixes the webs 22 on the bush 23 a quantity of lifting knives 8 are allocated to each pair of knife units 6 7 as is seen in fig2 and 6 the individual lifting knives are connected to the knife units by retainers or holders 30 the lifting knife 8 is fixedly connected to holder 30 and the holder is linked to the knife unit each lifting knife 8 is guided in a guidance device or arrangement 31 so that said knife 8 performs a straight line up and down movement this prevents an excursion of the hooks not shown engageable by the lifting knife 8 the guiding arrangement 31 consists of a plate 32 which is fastened at the outer side of the frame shields 2 3 slots 33 are configured in the plate 32 through at least which the ends of the lifting.