I've heard it said by a number of super-indie shooters that the only thing that you need to shoot a movie is a camera. This is true but the idea of shooting without a truck full of C-Stands seems really daunting.
Arguably the most versatile piece of film support equipment, the Century Grip Stand goes back to some of the earliest days of film making. It's been in use for over one hundred years and some even go so far as to say that Edison, himself invented them, though I doubt that's true.
Expressly, they're for one of two purposes, holding very small lights and for holding the things that then manipulate that light. In my experience, light heads small enough to be safely mounted on a C-stand like Inkys and Jokers aren't used that often so the Electrics only have a handful of these. The Grip department, however, will likely have dozens, if not hundreds, of these devices.
Generally, C-stands hold flags, nets, frames, kookalorises, mole trees and all the other grip equipment used in painting with light. More prosaically, I've seen them used to build courtesy tents, hold up portable sound studios, prop up false walls, hold monitors, create cyc screens, mock up false windows, grip boom poles and place hold for actors' eyelines.
No other device rivals the C-stand for versatility. In fact, I've heard it said that it came to be called the "Century" stand because it can be configured in over 100 distinct ways.*
In terms of construction, it's a simple set of telescoping cylinders on top of a tripod. The legs of the tripod are each a different height to facilitate putting a number of stands in close quarters. At the top is a standard grip pin. Generally a gobo head and arm are attached to the pin.** When all three risers are extended and the arm vertical they approach thirteen feet in height. The whole thing then collapses flat for easy transport and storage. Additionally, there are a handful of variations on the C-stand for particular applications. A "Gary Coleman" is a miniature C-stand, only two feet or so high, for instance.
I cannot overstate the importance of this piece of equipment. If you're in film school, familiarize yourself with this bit of gear. If you're thinking about starting a production company, get some of these. They're one of the few pieces of equipment that can be picked up relatively cheaply. If you're in a production office talking to the rental house and you can't get in touch with your Key Grip to find out if the order is exactly what he specified, always default to a half dozen extra. C-stands, when in abundance, can substitute for at least a dozen other pieces of equipment but absolutely nothing is an adequate substitute for the C-stand. One day, when I no longer have to share an office, I will build my shelves and floor lamps from C-stands and my desk from Apple Boxes just to impress on others how vital this kind of equipment is. Am I making sense here?
The very practices of Gripping and Gaffing are predicated on the assumption that there are plenty of C-stands go go around. Excepting Apple Boxes, they are the most ubiquitous item on a professional film shoot. All other pieces of film gear are designed to interface with them. They are such a staple of the industry that trying to light a movie without them would be a bit like trying to make a cake without mixers or spatulas.
Speaking of which, Apple Boxes, but that's a screed for another time.
*The name actually comes from the original C-stands extending to 100 inches in height.
**Technically, the gobo arm and the stand are separate bits of gear but they are so often sold, used and stored in this configuration that they are assumed to go together, even though the arm has many other uses independent of the stand, itself.