embodiments the sliding junction is provided relative to the rear binding the sliding junction may be transferred to the front binding simply by reversing the orientation of the beam so that the sliding slot is provided at the front mounting plate as is shown in fig1 a b in the fixed mode the region of the ski under the binding is stiffened sharply reducing the flex at the central region of the ski while accentuating the flex of the tail region of the ski the consequence is a dramatic arc in the tail to maintain the ski in a fixed mode the rear mounting plate is prevented from axially traversing the binding plate beam a flex inhibitor is provided in the binding mount assembly to disable the sliding junction in one arrangement the flex inhibitor includes complementary throughholes 190 192 in the sidewalls of the mounting plates and in the binding plate beam which are dimensioned to receive locking pins 194 181 see fig2 d and 6 markings may be provided on the edge or upper surface of the binding plate to facilitate registering the bindings and mounting plates the pin may be friction fit through the beam and mounting plate or threadably engaged to the openings in the mounting.