We would need a large number to hold these off, form a barrier.

Whether this will form an effective barrier, no one knows.

The door still formed a barrier, though force could break it down.

Her past formed a barrier between them that would always be there.

But their trunks were never so close as to form a barrier.

Indeed, the powerful black center formed a perfect barrier against attack.

They might have formed a barrier between him and the monster.

The hills, due to their complexity and position form a barrier between the two countries.

The ground could be made to rise up and form a barrier that prevented them from leaving.

Hills form a natural barrier on its northern and western sides.