Note 3 - Revenue Recognition - Disaggregation of Net Sales by Product Line (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 28, 2019	Dec. 29, 2018
Revenue	$ 97,569	$ 104,110
UNITED STATES
Revenue	97,257	103,621
Non-US [Member]
Revenue	312	489
Welded Wire Reinforcement [Member]
Revenue	61,827	66,278
Prestressed Concrete Strand [Member]
Revenue	$ 35,742	$ 37,832

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

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