These can be built in three sizes: buckler (12in or less across its longest dimension), small (2ft or less across its longest dimension), or large (any size, provided that it is safe and properly constructed). Shields are considered to be one-handed weapons, and their edges must be covered with pipe foam. The face of the shield may be covered with soft foam, duct taped, or painted, but cannot have hard or pointed projections of any kind. Shields may only be used to block incoming attacks and projectiles, and must never be swung at an opponent or another shield.
In the Star Trek fictional universe, the reference to shields typically relates to a 23rd & 24th century technology that protects starships, space stations or planets from damage by natural hazard or enemy attack. Synonyms include deflectors, deflector shields, or screens.