### Question
How is the term usable space defined?


### Answer
The term **usable space** is defined in *47 U.S.C. § 224* as the following:

> the space above the minimum grade level which can be used for the attachment of wires, cables, and associated equipment

#### Citation:
  - *47 U.S.C. § 224*
  - Heading: **CHAPTER 4-RADIO ACT OF 1927 > SUBCHAPTER II-COMMON CARRIERS**

