Horizontal lines run left to right, parallel to the horizon, with slope 0 and equation y = k. Vertical lines run top to bottom, perpendicular to the horizon, with undefined slope and equation x = k.

Whether you are sketching graphs in mathematics, understanding directions in geography, or reading blueprints in design class, horizontal and vertical lines are concepts you cannot avoid. They form ...

When you're ready to have employees sign on the dotted – or not so dotted – line, you need to point out where they should actually place their John Hancocks on your document. With Microsoft Word, it's ...