roof surface 10 has an opening the boundary of which is lined by a personnel access hatch frame 11 to one side 12 of which a closure panel shown in outline 13 is hingedly mounted by hinges 14 whereby it may move between an open position as shown and a closed position in which it closes and seals the opening defined by the frame 11 the safety rail installation for the personnel access hatch comprises four vertical posts 20 each having a lower end received in and secured in known manner in a socket 21 formed integrally with an end flange 17 that is secured by countersunk screws to the upper surface of a rectangular foot plate 22 the flanged socket 21 is shown in more detail in fig2 each support post 20 and foot plate 22 lies free standing on the roof surface 10 two of the posts 20 at one side 30 of the frame are interconnected by a rigid upper guard rail 25 and a rigid middle guard rail 23 the rails 23 25 extending horizontally the rails are secured to the posts by rigid tube connectors 26 27 of a kind known per se and shown more clearly in fig3 the connectors 26 27 are each of a two way offset cross u2014 over type available as type 45 from kee klamp limited the offset connectors are positioned such that the horizontal rails 23 25 lie outwards of the posts 20 as considered.