Tok'ra force field

"They work one way. They keep things in, not out."

- Major Samantha Carter

Tok'ra forcefields, also referred to as shields, are energy barriers, unique in that they are one-way in nature, allowing matter to enter the shield in one direction, but not the other.

Several variants of the shield appear to exist. In one variant, an enclosure is formed around an area in the shape of a cube. When this variant is activated, it appears initially as a thin beam emitted from a single point and extending vertically up to a maximum height. This vertical beam then moves in a straight line until a square is fully traced out. Another variant takes the form of a flat wall projected by a series of emitters.

These forcefields are often used in traps; In 2003, a Tok'ra forcefield was used in an attempt capture and incapacitate a Kull warrior. However, due to the nature of the Kull's armor, it was able to penetrate the shield with relative ease. Additionally, these forcefields have been used to detain individuals, being placed at the doorway of a room to prevent an individual from leaving. In 2005, a Tok'ra forcefield was used to detain Khalek, though he too was able to penetrate it using abilities gained through the ascension process.