but the lug grooves 32 33 can also be of same size the size of the recess 31 is corresponding to the space to be taken by the insert 20 with the rod 10 added with the material thickness t so that the insert 20 will accommodate tightly the recess 31 of the holder 30 and to lock the rod 10 when placed the holder 30 is of composite material or of polyethene the holder 30 can be attached to the sizer or the coater by manners known as such to one skilled in the art as can be seen from fig2 a 2b the insert 20 and the holder 30 are elongate profiles the length of which will extend at least over the width of the fiber web to be sized or coated so that the over the same fiber web width extending rod 10 is able to dose the sizing medium or the coating medium on the width of fiber web in fig3 a 3d are shown schematically steps of assembling one example of the rod bed assembly as shown in fig3 a first one side of the insert 20 is inserted into the groove of the holder the other side of the insert 20 is slightly pressed and simultaneously the insert 20 is further inserted deeper into the groove of.