COSTS AND ESTIMATED EARNINGS IN EXCESS OF BILLINGS, NET (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
COSTS AND ESTIMATED EARNINGS IN EXCESS OF BILLINGS, NET (Details) [Line Items]
Revenues	$ 11,672,000	$ 9,628,000	$ 38,612,000	$ 31,270,000
Loss on Contracts	144,000	290,000	876,000	2,400,000
Contracts Accounted for under Percentage of Completion [Member]
COSTS AND ESTIMATED EARNINGS IN EXCESS OF BILLINGS, NET (Details) [Line Items]
Revenues	$ 10,800,000	$ 8,500,000	$ 35,600,000	$ 28,500,000