Rare term for a zipper; the common word is ファスナー or ジッパー. 線ファスナー is a literal kanji compound (線 = line) that is not widely used.
See also: ファスナー
This old dictionary has an entry for '線ファスナー'.
Compound of 線 (sen, 'line') and ファスナー (fasunā, 'fastener'), literally 'line fastener'. The exact origin is uncertain; it may be a direct translation or an older coined term that did not become common.