Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Apr. 30, 2020	$ 9,164	$ 56,914	$ (12,137)	$ (195)	$ 490	$ 54,236
Balance (in Shares) at Apr. 30, 2020	9,163,940			42,696
Contribution of stock to 401(k) plan		68		$ 68		136
Contribution of stock to 401(k) plan (in Shares)				(14,926)
Stock-based compensation expense		54				54
Exercise of stock options and stock appreciation rights - net of shares tendered for exercise price		(109)		$ 109
Exercise of stock options and stock appreciation rights - net of shares tendered for exercise price (in Shares)				(23,808)
Other comprehensive income (loss), net of tax					171	171
Net income (loss)			(262)			(262)
Balance at Jul. 31, 2020	$ 9,164	56,927	(12,399)	$ (18)	661	54,335
Balance (in Shares) at Jul. 31, 2020	9,163,940			3,962
Balance at Apr. 30, 2020	$ 9,164	56,914	(12,137)	$ (195)	490	54,236
Balance (in Shares) at Apr. 30, 2020	9,163,940			42,696
Net income (loss)						67
Balance at Oct. 31, 2020	$ 9,176	57,071	(12,070)	$ (6)	485	54,656
Balance (in Shares) at Oct. 31, 2020	9,176,090			1,376
Balance at Jul. 31, 2020	$ 9,164	56,927	(12,399)	$ (18)	661	54,335
Balance (in Shares) at Jul. 31, 2020	9,163,940			3,962
Contribution of stock to 401(k) plan	$ 9	86				95
Contribution of stock to 401(k) plan (in Shares)	9,496
Stock-based compensation expense		73				73
Exercise of stock options and stock appreciation rights - net of shares tendered for exercise price	$ 3	(15)		$ 12		0
Exercise of stock options and stock appreciation rights - net of shares tendered for exercise price (in Shares)	2,654			(2,586)
Other comprehensive income (loss), net of tax					(176)	(176)
Net income (loss)			329			329
Balance at Oct. 31, 2020	$ 9,176	57,071	(12,070)	$ (6)	485	54,656
Balance (in Shares) at Oct. 31, 2020	9,176,090			1,376
Balance at Apr. 30, 2021	$ 9,226	57,355	(11,457)	$ (6)	291	55,409
Balance (in Shares) at Apr. 30, 2021	9,226,268			1,376
Contribution of stock to 401(k) plan	$ 13	117				130
Contribution of stock to 401(k) plan (in Shares)	13,251
Stock-based compensation expense	$ 8	61				69
Stock-based compensation expense (in Shares)	7,500
Other comprehensive income (loss), net of tax					79	79
Net income (loss)			(1,575)			(1,575)
Balance at Jul. 31, 2021	$ 9,247	57,533	(13,032)	$ (6)	370	54,112
Balance (in Shares) at Jul. 31, 2021	9,247,019			1,376
Balance at Apr. 30, 2021	$ 9,226	57,355	(11,457)	$ (6)	291	55,409
Balance (in Shares) at Apr. 30, 2021	9,226,268			1,376
Net income (loss)						(1,078)
Balance at Oct. 31, 2021	$ 9,264	57,693	(12,535)	$ (6)	213	54,629
Balance (in Shares) at Oct. 31, 2021	9,264,326			1,376
Balance at Jul. 31, 2021	$ 9,247	57,533	(13,032)	$ (6)	370	54,112
Balance (in Shares) at Jul. 31, 2021	9,247,019			1,376
Contribution of stock to 401(k) plan	$ 11	100				111
Contribution of stock to 401(k) plan (in Shares)	10,779
Stock-based compensation expense		66				66
Stock-based compensation expense (in Shares)	250
Exercise of stock options and stock appreciation rights - net of shares tendered for exercise price	$ 6	(6)
Exercise of stock options and stock appreciation rights - net of shares tendered for exercise price (in Shares)	6,278
Other comprehensive income (loss), net of tax					(157)	(157)
Net income (loss)			497			497
Balance at Oct. 31, 2021	$ 9,264	$ 57,693	$ (12,535)	$ (6)	$ 213	$ 54,629
Balance (in Shares) at Oct. 31, 2021	9,264,326			1,376