A lamp socket or holder is used to secure a light bulb into a light fixture and to deliver electric current through a positive terminal and a ground terminal of the bulb to trigger illumination of the bulb. The lamp holders are engineered to physically and electrically engage with sockets which extend from the electrical cord. A range of lamp holders are offered on the market. They are manufactured to hold lamps in screw bases, twist & lock bases, bi-pin bases, plug-in lamp bases. Typical screw bases include E10 (Mini screw), E11 (Mini candelabra), E12 (Candelabra), E14, E17 (Intermediate), E26 (Medium standard), E27 (Medium), E39/E40 (Mogul). GU10 and GU24 are twist and lock bases. Bi-pin bases include G4, GU4, GU5.3, GY6.35, GU8, GY8, GY8.6, G9, G12. PL lamp bases include G24q, G23, GX23, G24d, GX32d, 2G7, 2GX7, 2G11, GX10q-4. A luminaire using a straight tube type fluorescent lamp including G13 bi-pin (T8 tubes) and miniature bi-pin G5 (T5 tubes) bases each having a pair of lamp pins featuring a circular shape in cross-section and projecting therefrom at both ends thereof, and sockets for connecting the fluorescent lamp is commonly used. A typical light fixture for a bipin-base tube lamp has a pair of lamp holders between which the lamp fits. Each holder has a housing which includes a mouth and a rotor rotatably supported in the housing alongside the mouth and having an installation slot for receiving contact pins of the fluorescent lamp.