"What do you mean it doesn't fit!"

The designing phase of a project is a dynamic and creative period in creating a new product. SolidWorks has always paid close attention to the designer, and they understand the controlled chaos in the designing/brainstorming phase. SolidWorks 2009 now offers what are called sensors. Sensors were added to SolidWorks to more or less set ground rules and design criteria, to aid a designer in keeping within certain goals. If a part must be designed to fit into a small area for example, the designer can set a sensor to monitor the overall area, length or volume that the part occupies, to save them from having to remember the constraint while designing. 

Sensors can be applied to a myriad of different properties in a part file, overall volume, surface area, mass, and overall length. This is not limited to part files; sensors are also available in assemblies, and FEA analysis to notify a designer if parts are interfering, or of certain levels of stress, strain, and displacement have occurred during the course of a physical simulation. If used correctly sensors will add a great deal to the efficiency of the most important phase of the design process.