Drilling into RSJ?

The_Governor

I wanted to get some advice before I break out my big tools

I'm having to rehang blinds after having our windows replaced. Previously I hung the blinds off the window frame, but that isn't an option on the new ones.

So, I thought I can hang them from the just above the window, within the window portal. But, when I drilled up into the plaster I hit what I think is the steel joist, with only a 20mm gap between it and the plaster below it.

Should I just drill straight through the steel, or are there short, but grippy Rawlplugs I can use?

I'm guessing anyone that hangs venetians from above has this same problem in modern houses?

The_Governor

Thanks Andy much obliged.

I am of course assuming it is steel and not concrete as I can't see it!