Selecting The Appropriate Fixture
There are a variety of fixtures from which you can choose depending on the hardware on the lamp base. Below are the options.
Washer Top - sets on a harp and is secured with a finial
Clip top - clips over a standard size light bulb
Torpedo/Candleabara clip top - clips over a tapered bulb
Uno Bridge - screws right to the socket and allowing the lampshade to hang down from a bridge arm.
Chimney top - slips down over a glass chimney on an electrified hurricane lamp.