I'm trying to replace the socket in an old desk lamp, and I need to pull the wire through. However, the wire is secured tightly by a black plastic clip at the base. I'm wondering what this clip is called, and how to remove the wire without breaking the clip. I would like to be able to reuse the clip (or buy a new one if I know what it's called and can find it).
That is a Heyco bushing. You need to squeeze, preferably with a needle-nose pliers, in what I would call a top-to-bottom position considering the orientation of how it is installed.
If you squeeze just right it will come out no problem and will not damage the cord.
Here is a decent video explanation: http://youtu.be/G1IWQB3mQrw
Here is the manufacturer's guide: http://www.heyco.com/img/SR_Assembly_Guide.pdf
Rest assured, it CAN be done with a regular pliers if you're careful. I've done it a million times.
Also, keep in mind, to replace a socket you really should not have to remove that bushing if the cord is in good shape.
Speedy's answer is an excellent one. I here want to add a picture of what these clips look like in the raw so that it is more apparent how they work.
The groves along the areas pointed to by the red lines are those that grip to the inside edge of the hole in the lamp base and retain the cord. When you squeeze the clip, as Speedy explains, the clip compresses enough to release the grooves from the inside edge of the hole in the lamp base.
