Consider the angles created when two perpendicular walls meet.

Do this by moving the window closer to an adjacent perpendicular wall.

Along the edge of the sea the cliff rose in an unbroken, perpendicular wall.

Almost touching our knees, a perpendicular wall of mail matter rose up to the roof.

Hall was leading Billy up what seemed a perpendicular wall in order to gain the backbone of the rock.

It's very deep in proportion to its width and has perpendicular walls, so that you don't see it till you're almost on the edge.

Nothing human could have clung to that perpendicular wall.

This valley is closed at the east by a perpendicular wall more than 2,000 yards high.

The spin will cause the ball to leave the opposite wall almost perpendicular to it.

It was a perpendicular wall of very hard granite, which even the waves had not worn away.