Fixing Top Rail for Folding Doors - What Fixings to Use? General problems, solutions, information and advice on fixing to walls of all kinds

[Tonyonly]

I have to fix a metal top rail to an opening that was for a patio door before an extension was added to my bungalow. The bungalow was built in 1969 and I know the outer skin has a steel RSJ and I assume the inner skin is a concrete lintel. The manufacturer recommends three inch screws "in appropriate fixings". I will try a masonry drill but what fixings should I use? The rail has to take the weight of three doors. Hope someone can help.
Tonyonly

[welsh brickie]

you can use 50mm stardrive fixings, really strong no rawplug required, with 75mm screw it might hit the reinforcing,you will need a cordless to screw them into position