指定用于屏蔽外壳构造的各种引线单元的属性:基本单元（砖、柱）和功能单元（孔砖、窗、球体单元、插头和异径单元）。只有一块和两块V形砖是标准化的。这些单元分为三类:标准化单元；在一个国家使用频率很低或用于非常特殊的目的，或使用频率很高的装置，并认为这种使用将变得更广泛；过渡期可接受的单位。

Specifies the properties of the various lead units used in the construction of shielded enclosures: basic units (bricks, posts) and functional units (aperture bricks, windows, sphere units, plugs and reducing units). Only one and two chevron bricks are standardized. The units are classified into 3 categories: standardized units; units which are either used very infrequently or for very specialized purposes, or are used very frequently in one country and it is felt that this use will become more widespread; units which are acceptable for a transition period.