How can I safely open, wire & close this E27 lamp holder?
Slide a flat-bladed screwdriver into a rectangular hole in the back (rounded) end. Pry the inner (deepest) end of the locking tab outward gently while applying pressure to separate the bulb socket from the back cover at the joint that jogs its way around the middle. If you're not able to release the tab from the back, use a knife point from the outside, prying the tip of the tab outward.
When it releases slightly, do the same on the other side to fully release the back cover. You may want to slip a folded paper or other tool in the gap after you release the first tab to maintain separation.
Slide the wires through the back cover ports, make the connections, and snap the cover back on, making sure that both tabs engage.

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