-> "A Garnishee Order is an Order freezing money owed to the Debtor by another person."
http://www.lawcentre.co.uk/civil_disputes_in_cc/s3l.htm

However, a garnishee order can be made in respect of any assets, not just money.

-> "garnishee order - An order made by a judge on behalf of a judgement creditor restraining a third party (often a bank), called a garnishee, from paying money to the judgement debtor until sanctioned to do so by the court. The order may also specify that the garnishee must pay a stated sum to the judgement creditor, or to the court, from the funds belonging to the judgement debtor."


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Note added at 2002-11-07 15:34:26 (GMT)
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Van den End\'s Juridisch Lexicon gives \'prejudgment attachment/seizure, attachment/seizure before judgment\' for \'conservatoir beslag\' and \'to attach/seize before judgment\' for \'conservatoir beslag leggen\'. While I wouldn\'t question the correctness of the meaning, I think an English-speaking lawyer could question his mastery of legal idiom.

In a notification to a bank asking/instructing them to \"seize before judgment\" you would most likely actually ask them to \"freeze the assets belonging to xxx persuant to garnishee order xxx issued by court xxx\" and enclose the garnishee order.