56. An employer shall ensure that, where a scotch and guy derrick crane is to be used,

(a) the jib of a scotch derrick crane is not erected between the back stays of the crane,

(b) a load which lies in the angle between the back stays of a scotch derrick crane is not moved by that crane,

(c) appropriate measures are taken to prevent the foot of the king post of any scotch derrick crane from being lifted out of its socket or support whilst in use, and

(d) where the guys of a guy derrick crane cannot be fixed at approximately equal inclinations to the mast so that the angles between adjacent pairs of guys are approximately equal, such other measures are taken as will ensure the stability of the crane.