Whether you're mounting fixtures, installing shelving, or hanging artwork in your home, it's critical to ensure the item is perfectly level. While traditional bubble levels are useful for quick checks ...

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.

A beam or "girder" bridge is the simplest and most inexpensive kind of bridge. According to Craig Finley of Finley/McNary Engineering, "they're basically the vanillas of the bridge world." In its most ...