Our missile had work platforms that would lower from the wall in six sections for each level, all with the grating you describe. If they had too many platforms down, it would take the missile off alert (bad thing!). So, MX would come out and put up posts and chain railings to border partial sections lowered... NO FRICKING WAY! The grates would jiggle a little and the chain looked like nothing at all to stop you from falling ten stories.
I never made it all the way out on one of those.
That said, I was always mesmerized by the rear end of a C-130 with the ramp down in flight. I could sit back there holding on to the seat webbing and felt safe as can be, even though I wasn't tied off.