11.   Levels can also be used to indicate whether a vertical surface is perpendicular, or plumb, with the horizontal plane.

12.   Mice can quickly scale vertical surfaces.

13.   Q. What is the adhesive power of mortar, especially on a vertical surface?

14.   Prop up a board so you have a vertical surface.

15.   Set in a vertical surface, such as a chimney or wall, it can last for centuries.

16.   She finds a vertical surface, a tree, and sits urinating the unneeded blood for an hour.

17.   Small clinging birds such as chickadees, nuthatches, titmice, woodpeckers and wrens will find it easy to cling to the vertical surface.

18.   Small lizards called geckos can climb a vertical surface at a speed of more than a yard per second.

19.   They decorate every vertical surface, including light poles, trees and electrical conduits, with their names.

20.   They have tiny legs, seldom walk and cannot perch, but cling to vertical surfaces.