RUG (שְׂמִיכָה, H8526, meaning uncertain, but some kind of covering). This word, used only once in the OT, identifies the article used by Jael the Kenite in covering Sisera who had fled from battle with Deborah and Barak and sought refuge in her tent (Judg 4:18). It may have been a mantle, a rug, a blanket, a cloak, etc. KJV tr. MANTLE; ASV, RSV, RUG; BDB suggests “rug or thick coverlet.”

International Standard Bible Encyclopedia (1915)

rug: Alternative rendering of a word (semikhah) in Jud 4:18 the Revised Version (British and American), "mantle" the King James Version. The translation is doubtful; Oxford Hebrew Lexicon; see Brown, Driver, and Briggs gives "rug or thick coverlet (?)."