Note 4 - Revenue Recognition - Disaggregation of Net Sales by Product Line (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 28, 2020	Mar. 30, 2019	Mar. 28, 2020	Mar. 30, 2019
Revenue	$ 114,859	$ 111,948	$ 212,428	$ 216,058
UNITED STATES
Revenue	114,549	111,620	211,806	215,241
Non-US [Member]
Revenue	310	328	622	817
Welded Wire Reinforcement [Member]
Revenue	69,355	68,941	131,182	135,219
Prestressed Concrete Strand [Member]
Revenue	$ 45,504	$ 43,007	$ 81,246	$ 80,839