1.   In recent decades, those invisible walls no longer hold.

2.   Lately, Capriati has found it difficult to build an invisible wall between herself and the distractions.

3.   Regulators and top officers of brokerage firms bear some of the blame for not maintaining the invisible wall between investment banking and research, according to Hendler.

4.   Space -- empty space -- will act as invisible walls.

5.   The insecticide creates an invisible chemical wall that keeps the bugs away.

6.   The more dangerous walls are the invisible walls.

7.   Unlike typical driving games, you are not confined to a small area by invisible walls or massive obstacles.