Check through all his employment papers to see if he "agreed" to deductions for equipment replacement, breakage, reimbursement for accidents, etc., where he was at fault, when he started working there. If he did not do so in writing, then he should tell the company that he wants that money back because what they did was illegal. They are only allowed to deduct taxes, authorized union dues, court ordered garnishments, authorized insurance payments, etc. The word is "authorized." If he doesn't get this money back, then you should contact your State's wage & hour division and file a complaint.