Note 3 - Revenue Recognition - Disaggregation of Net Sales by Product Line (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Revenue	$ 126,252	$ 126,688	$ 342,310	$ 331,846
UNITED STATES
Revenue	125,929	126,299	341,169	330,513
Non-US [Member]
Revenue	323	389	1,141	1,333
Welded Wire Reinforcement [Member]
Revenue	80,007	76,756	215,226	198,453
Prestressed Concrete Strand [Member]
Revenue	$ 46,245	$ 49,932	$ 127,084	$ 133,393

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration