A few more reasons why it is wrong: Take a look at NEC 200.9. It says that a white wire (grounded) is to be attached to a white colored screw. Connecting the load side of the circuit to the screw shell base would be considered a hot conductor.[:-thumbd] Also, take a look at the rating of a lamp socket. They are rated at 660 W. That is 5.5 A @ 120 V. If I was to be using a lamp socket for as a fuseholder with a 15 amp fuse installed like in the picture and "protecting" a branch circuit, I would be overloading the socket. If you look at a "buss door fuse holder" they are rated at 15 A. A fuseholder in a fused panelboard is rated 30 A (Edison Base) Also, Show me in the code book where it says that I need to protect the doorbell transformer with a 3 A fuse. We have been installing them right into a KO in the panelboard itself, and pigtailing it to a 15 A circuit for many years.