It's big different to wire a ceramic e27 lamp holder, or metal lamp holder, or plastic lamp holder, the wire connection system are different.

1. For example, the vintage ceramic lamp holder, there is a lock inside for safety, you have to use a screw driver to press the copper part down before you take the porcelain ring off, and then put a cable grip on the M10 metal thread for wire holding, after these process, you can put the wires through the cable grip to the wire terminals inside accordingly.

2. Regarding the wire connection to plastic lamp holder, there are 3different connection systerm usually:

A. connection system like the above porcelain lamp holder E27,  then connect the wire as above process accordingly.

B. If it's thermal plastic lamp holder, then usually you just need to take off the cap first with a screw driver, and then put a cable girp on the M10 thread, finally you just need to insert the wires to the clamp inside, then it's done.

C. It's the easiest model for wiring, just put the product up side down, connect the wires to the terminals at bottom, then it's done.

3. About the vintage metal lamp holder, there are two different connection system popular:

A. the metal lamp holder with a porcelain core inside or plastic core, first you have to use a screw driver to press down the lock inside to take off the metal body, and then put a cable grip on the M10 thread.

B. At present, the present popular models of vintage industrial metal lamp holder for pendant light and ceiling lamp, usually are made from aluminum housing with plastic socket inside.

First, take off the plastic socket from the aluminum housing,

Second, open the cap of plastic holder with a screw driver, or unscrew the cap

Third, put the wires through aluminum body, and then insert the wires to the plastic lamp socket inside or connect to the terminals inside.