of the rails 115 and 116 of the ladder is provided a tubular receptacle 130 131 for a curved post 132 and 133 respectively which extends upwardly from the receptacle and forwardly beyond the end of the upper part of the ladder to the upper anchor 112 113 respectively thus the anchors are cantilevered forwardly beyond the end of the ladder by the curvature of the posts 132 and 133 thus again the anchors 112 and 113 are located approximately over the midline of the base and a cantilevered over structure with the base located underneath the structure again this arrangement is particularly suitable for the wing of an aircraft where the base can be moved to a position beneath the wing with the platform moved up to the end of the wing and the anchors 112 and 113 located over the wing for the operator to transfer from the platform onto the wing for operations on the aircraft in fig4 is shown an alternative arrangement which utilizes basically the structure of fig3 arranged in a pair of such structures connected together by cross members 140 and 141 thus each base 100 and each support 111 is provided at a position spaced transversely of the base frames and connected together at spaced positions by the rails 140 and 141 at the top of the post 132 and 133 is provided a transverse rail 136 similar to the rail 36 which carries a track 137 and trolleys 138 each trolley is attached to a personal safety arrest system generally indicated at 145 thus the basic system shown in fig3 can be modified to provide an elongated structure to provide an.