Inventories (Details) (USD $)	Sep. 28, 2012	Dec. 30, 2011
Inventory Disclosure [Abstract]
Aluminum and steel coil	$ 67,711,000	$ 52,681,000
Raw materials	14,591,000	12,808,000
Work in process	2,309,000	2,980,000
Finished products	16,219,000	14,927,000
Inventories, net	100,830,000	83,396,000
Inventory valuation reserves	$ (2,800,000)	$ (3,000,000)