About "Where Is That Darn Switch"

Where: interrogative adverb 1 in or to what place or position?
Is: 3rd person singular present of be.
That: demonstrative adjective 1 designating the person or thing indicated, named, understood, etc.
Darn: adverb colloquial = DAMN (in imprecatory sense).
Switch: noun 1 a device for making and breaking the connection (in an electrical circuit).