Closed stairs with chain.

[tufguy]

"Tom lives upstairs and he has attached a chain to the stairs railing to block the way of the person whoever wants to go upstairs without his permission. He closes the stairs with help of that chain."

Please check.

 

[Tarheel]

Perhaps:

Tom has put a chain across the stairs to block anybody who wants to use the stairs without his permission.

 

[Raymott]

"Tom has put a chain across the stairs to block anybody from using them without his permission."
I don't think 'stairs' needs to be repeated. It's done its job.

 

[Raymott]

Thanks. It really annoys me when other people do that! But it's an easy mistake to make when you're tired or off your guard for some reason.
In this case, I think it was perseveration from the first "It's".