Flat-Space technology is a form of dimensional compression technology seen in the movie Ultraviolet.
This form of dimensional compression is used to store objects in a pocket dimension. Simple objects are stored/retrieved and more complex ones systematically deconstructed/reconstructed in a flow of sparkling lights. A significant number of items can be stored for easy retrieval without burdening the user with either weight or size. The technology mainly takes the form of easily overlooked wristbands, although one-inch scabbards holding 42-inch swords are also seen. Handguns (some with 18-inch swords stored in their six-inch grips with enough room remaining for great amounts of ammunition), and ammunition are also hidden in this manner (the bullets flying from the wristbands into the magazines on command).
The technology is also used to create habitable pocket dimensions, such as the briefcase/backpack used to transport the ten year old Six and the semi trailer with the internal dimensions of a warehouse (containing Garth's research lab and armory).
Dimensional compression is the basis of one of the light hearted scenes in the movie. A security scanner checks Violet, saying "Number of weapons found:", pauses shortly as Violet's weapons are displayed, and finishes "many", as it is unable to calculate the exact number.