Glue sagging wallpaper border back up?

Question

What is the best way to glue sagging wallpaper border back up?
It is the type that comes with the adhesive already on it, and it's losing the stickyness and coming off.

Answer 1

Prepasted wallpaper or borders are never very good or long
lasting. Purchase a wall paper paste, smallest size avail,
mix according to directions or I believe there are pre-mixed
available on the market now. Place the paste on the back of
the border and smooth it back into place.

Answer 2

They make a product especially for borders. Check your local paint and paper store. They should carry it.