Replacement tap with stiff swivel spout mounted on metal sink basin using the one bolt provided. Bolt tightened up. No other restraint as I had to use flexible pipes on new tap to be able to fit it. Monbloc unit not held fixed and moves when spout moved between the two basins..... Single bolt fixing appears standard - any ideas as to how (1) I can secure tap or (2) how you ease rotating spout?