A flat board as a base plate of binding for splitboards with holders for its fixation on skis joined into a snowboard has a circular slit formed in the central part of the board. The circular slit is equipped with a perimeter recessing for demountable fixing of a contact ring which is on its inner perimeter equipped with two couples of opposed dents designed for connection with a holder. The contact ring is also modified between the dents for insertion of end pins of locking eccentric. The locking eccentric is formed by an axial shaft with end pins protruding from end hubs formed at the both ends of the axial shaft.