to the crossarm 14 within base 13 is a recess 15 which faces the same direction as hook 12 see fig1 recess 15 lies beneath hook 12 and is formed by the side and rear walls of base 13 along the top of crossarm 14 at equally spaced intervals are apertures 16 extending downwardly from crossarm 14 are end panels 18 and side panels 20 all of which are joined to form a hollow trough beneath the crossarm said trough housing operating bar 22 clamps 24 are 34 l 34 shaped such that their horizontal legs 26 lie above and are parallel to the crossarm 14 and their vertical legs 28 extend downwardly through apertures 16 and are fastened to operating bar 22 see fig2 thus it will be appreciated that as operating bar 22 is raised horizontal legs 26 are lifted off crossarm 14 to their open position and when the operating bar is lowered the legs close upon the top of crossarm 14 the portion of the horizontal legs 26 and the crossarm 14 which are pressed together are both covered with felt 25 at either end of operating bar 22 is a spring socket 30 a spring 32 is set in each socket 30 so as to expand between crossarm 14 and operating bar 22 thereby biasing the operating bar.