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REVENUE RECOGNITION - Percentage of completion (Details) - USD ($)
$ in Thousands
Mar. 27, 2021
Dec. 26, 2020
Mar. 28, 2020
REVENUE RECOGNITION      
Cost and Earnings in Excess of Billings $ 3,408 $ 4,169 $ 5,744
Billings in Excess of Cost and Earnings $ 9,396 $ 11,530 $ 9,920