E.V.S. is the fastest way to test devices that are required to be removed from the wall, in order to access the wiring so you can obtain: OPENS, GROUNDS, or SHORTS.
Once installed your testing time is reduced from several minutes to mere seconds.

The dust and water caps protect the E.V.S. from construction dust and water splash.
They can be left on after installation, if the environment the E.V.S. is installed in, is prone the excessive dust and or water splash.