NATURE OF OPERATIONS AND ACCOUNTING POLICIES. - Segment Info (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) item	Dec. 26, 2015 USD ($)	Dec. 27, 2014 USD ($)
Segment Information
Net sales	$ 298,971,665	$ 278,424,799	$ 236,308,920
Specialized Vehicles
Segment Information
Number of product categories | item	3
Net sales	$ 294,570,886	274,563,033	234,182,656
Specialized Vehicles | Trucks
Segment Information
Net sales	284,994,546	261,598,525	211,975,917
Specialized Vehicles | Trolley
Segment Information
Net sales	4,422,375	5,666,944	8,414,833
Specialized Vehicles | Specialty Vehicles
Segment Information
Net sales	5,153,965	7,297,564	13,791,906
Fiberglass Products
Segment Information
Net sales	$ 4,400,779	$ 3,861,766	$ 2,126,264