Income Taxes - Deferred Tax Assets (Liabilities) Related to Temporary Differences (Detail) - USD ($) $ in Thousands	Apr. 30, 2022	Apr. 30, 2021
Deferred Tax Assets, Net [Abstract]
Inventory reserves	$ 5,187	$ 4,508
Accrued expenses, including compensation	4,138	4,952
Net operating loss carryforwards and tax credits	3,168	3,189
Operating lease liability	866	1,132
Product liability	614	263
Workers' compensation	567	497
State bonus depreciation	787	888
Warranty reserve	1,111	1,303
Stock-based compensation	1,356	1,517
Other	973	1,292
Deferred Tax Assets, Gross, Total	18,767	19,541
Valuation allowance	(3,086)	(3,297)
Deferred Tax Assets, Net of Valuation Allowance, Total	15,681	16,244
Deferred Tax Liabilities
Operating lease right-of-use assets	(806)	(1,091)
Property, plant, and equipment	(12,049)	(13,994)
Intangible assets	(1,186)	(914)
Other	(419)	(1,149)
Deferred Tax Liabilities, Net, Total	(14,460)	(17,148)
Deferred Tax Assets, Net, Total	$ 1,221	$ 904