One classic style of hanging light uses a chain for support. The links of the chain can be removed in order to adjust the height. The cord is woven through the links and then passes through a small hollow nut at the mounting plate of the fixture. Chandeliers and hanging globes often have chain supports.
Pendant lights are often adjustable. Some models have multiple sections of hollow rods that thread together. You add or subtract sections to adjust the height, and the cord runs through the rod. Some pendants are adjustable through a counterweight system, which allows the lights to be adjusted at any time, even after installation. Some lights simply hang by their cords, although these models are often less expensive and are more susceptible to damage.
What is the best height for a light? The answer depends on many factors, including the light's intensity, the layout of the room and the location of the light. Lights above work spaces in the kitchen are typically 28 to 34 inches above the countertop. General lighting is often 72 inches off the floor. Lights above tables are often a little bit lower than lights above countertops.
Adjustable height fixtures are often used in bathrooms for accent or to put light closer to the sink or some other fixture. Any light chosen for a bathroom must be rated for a wet or damp environment. Also, any light chosen should be approved by the Underwriter's Laboratory and have a UL-listed rating. This listing ensures that the light has met stringent safety standards.