Spider lamp shades are the most common kind of shade for both floor and table lamps. The term spider lamp shade refers to the kind of fitting the shade has. The spider is a cross frame located at or near the top of the shade.
The term fitting describes how a lamp shade attaches to the lighting fixture. According to Lamps Plus, there are three kinds of lamp-shade fittings with the most popular being spider with harp.
To identify a spider lamp shade, look down at the top of the shade. A spider lamp shade will have a circular, washer-like piece of metal right in the center. The round piece of metal will have at least three spider-like arms that are attached to both the washer and the lamp shade.
The harp is an oval piece of wire that attaches to the lamp, goes up and around the light bulb, and has a screw on top that the spider shade lamp shade sits on. According to the Lamp Shade Shop, the harp is a support--on the lamp itself--that holds a washer-spider-type lamp shade in place.
A finial is a fancy bolt that attaches to the top of the harp, holding the spider lamp shade in place. Finials are the last piece attached to the top of the lamp and the spider lamp shade. Finials add a decorative finishing touch to spider lamp shades.
Stabilizer clips can be used to attach a spider lamp shade to other types of lamp-shade fittings--offering options beyond the harp fitting--like the slip uno fitting, which attaches at the light bulb's base.