Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Total Revenue	$ 9,544	$ 11,481	$ 28,502	$ 31,706
Cost of goods sold	6,951	8,303	21,508	22,361
Gross profit	2,593	3,178	6,994	9,345
Operating expenses
General and administrative expenses	1,305	1,383	4,059	3,840
Selling expenses	624	564	1,913	1,825
Total operating expenses	1,929	1,947	5,972	5,665
Operating income (loss)	664	1,231	1,022	3,680
Interest income (expense)
Interest expense	(44)	(44)	(135)	(135)
Interest income	10	9	29	28
Gain on sale of assets	51	15	106	32
Other income	11	11	30	35
Total other expense	28	(9)	30	(40)
Income before income tax expense	692	1,222	1,052	3,640
Income tax expense (benefit)	172	474	262	1,323
Net income (loss)	$ 520	$ 748	$ 790	$ 2,317
Basic and diluted earnings per share (in dollars per share)	$ 0.10	$ 0.15
Basic income (loss) per share (in dollars per share)			$ 0.16	$ 0.46
Weighted average number of common shares outstanding:
Basic (in shares)	5,080	5,054	5,078	5,036
Diluted (in shares)	5,099	5,099	5,098	5,075
Product sales
Total Revenue	$ 6,828	$ 9,295	$ 21,224	$ 21,853
Barrier rentals
Total Revenue	540	319	1,188	3,145
Royalty income
Total Revenue	465	483	1,193	1,387
Shipping and installation revenue
Total Revenue	$ 1,711	$ 1,384	$ 4,897	$ 5,321