Green’s Dictionary of Slang

(US) barbed wire.

1902		Yakima Herald (WA) 25 Nov. 4/2: The Prosser Telephone Company expects to attach their wires to the ‘bob’ wire fences.
1914		Deming Graphic (NM) 15 May 7/2: The fields under cultivation are being protected with rabbit-tight wire and bob-wire.
1921		Colville Exampiner (WA) 12 Mar. 9/2: Me and Jake [...] went out to Hendrixes woods [...] Got nothing but are pants torn on bob-wire.
1964		J. Thompson Pop. 1280 in Four Novels (1983) 425: Maybe the horse would [...] throw me into a bob-wire fence.
1993		R. Steagall ‘The Fence That Me and Shorty Built’ (poem) at RedSteagall.com 🌐 We’d picked up all the fencing tools / And staples off the road. / An extra roll of ‘bob’ wire / Was the last thing left to load.