"space rule" meaning in English

{
  "forms": [
    {
      "form": "space rules",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "space rule (plural space rules)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Printing",
          "orig": "en:Printing",
          "parents": [
            "Industries",
            "Business",
            "Economics",
            "Society",
            "Social sciences",
            "All topics",
            "Sciences",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A fine, thin, short metal rule of the same height as the type, used in printing short lines in tabular matter."
      ],
      "id": "en-space_rule-en-noun-h8TS20yK",
      "links": [
        [
          "printing",
          "printing#Noun"
        ],
        [
          "metal",
          "metal"
        ],
        [
          "rule",
          "rule"
        ],
        [
          "height",
          "height"
        ],
        [
          "type",
          "type"
        ],
        [
          "tabular",
          "tabular"
        ]
      ],
      "raw_glosses": [
        "(printing, historical) A fine, thin, short metal rule of the same height as the type, used in printing short lines in tabular matter."
      ],
      "tags": [
        "historical"
      ],
      "topics": [
        "media",
        "printing",
        "publishing"
      ]
    }
  ],
  "word": "space rule"
}

{
  "forms": [
    {
      "form": "space rules",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "space rule (plural space rules)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with historical senses",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Printing"
      ],
      "glosses": [
        "A fine, thin, short metal rule of the same height as the type, used in printing short lines in tabular matter."
      ],
      "links": [
        [
          "printing",
          "printing#Noun"
        ],
        [
          "metal",
          "metal"
        ],
        [
          "rule",
          "rule"
        ],
        [
          "height",
          "height"
        ],
        [
          "type",
          "type"
        ],
        [
          "tabular",
          "tabular"
        ]
      ],
      "raw_glosses": [
        "(printing, historical) A fine, thin, short metal rule of the same height as the type, used in printing short lines in tabular matter."
      ],
      "tags": [
        "historical"
      ],
      "topics": [
        "media",
        "printing",
        "publishing"
      ]
    }
  ],
  "word": "space rule"
}