Bx armor a neutral?
Just bought a house, about 70 years old. Parts of the home have knob and tube wiring. some has been changed to bx quite awhile ago it seems. Today I opened an existing junction box on the closet cieling hoping to add a light. Contained BX with a white and black wire ...both hot and no swtiches to be found. They were just capped off. I hooked the black light wire to the black ...when touching the white light wire to the bx shielding everything worked. Is this a trick they used years back? I've never seen it before. Doesn't seem safe to me but I have no idea. Any help would be appreciated. Thanks