passage 17 in each block the ends on both sides of the passage 17 are blocked by sealing screws 21 screwed in both ends of the block 8 when removing any mounting blocks 8 for replacement such blocks are just released from the connections with the race 12 by releasing the wedge block 30 and also with the fluid supply tubes 15 a wedge block 30 extends across the race 12 so that all of the series of mounting blocks 8 will be loosened upon prying the wedge block 30 upwardly to loosen it as will be understood by reference to fig4 the fluid supply tube 15 to any particular mounting block is disconnected by removing the threaded nut 32 and flat washer 33 which releases the tube from the fitting 16 as indicated in fig3 and 4 thus any individual block 8 may be removed to permit accurate alignment of auxiliary nozzles 2 in mounting thereof on the block 8 each of the nozzles 2 is provided with a base member 22 which is adapted to be engaged with the locating groove 24 at the bottom of block 8 so that the auxiliary nozzles 2 may be located relative to the weft guides 1 4 at a predetermined height and also at a proper angular position which is obtained.