manner as explained for fig8 and 9 fig1 15 illustrate a fifth embodiment again the configuration of the inner and outer laminates is similar to that of fig8 and 9 except that the channel portions overlying the inlet holes are configured to receive templates 54 templates 54 are secured as by welding to the inside of the outer laminates and so as to place a flap valve 56 of the template over each of the inlet holes 36 the flap valve being larger than the inlet hole as illustrated in the top of fig1 and in fig1 fluid pressure 42 forces the flap valve open and then due to the pressure within the channel the remaining valves are urged to a closed position the above embodiments are considered to be automatic versions of the invention in that an operator doesn 39 t have to make a determination of which inlet holes are to be blocked and which are left open the invention however contemplates improvements to the manual selection and blocking of the unused inlet holes which will now be discussed fig1 19 illustrate a first version of a manual embodiment of the invention this embodiment includes six inlet holes 36 for each channel 32 as can be seen in fig1 grooves or depressions 58 are provided in the center laminate which forms a passageway between the motor mount slot 60 and the inlet holes 36 cut off slide tabs 62 and a.