The act of selling and buying stocks almost instantaneously in order to increase or decrease book value. This is a routine method used by many investors and companies to change book values without changing beneficial ownership.

The directors were asked to confirm that no events had led to the crystallisation of any floating charges. 
(a floating charge is a security interest that hovers above the debtor's assets until some event causes the charge to become fixed or crystallized on those assets)
Investopedia Says:
An example of this occurs when an investor needs to take a capital loss for a particular stock, but still believes the stock will rise. Thus, he/she would crystallize the paper loss by selling the stock and buying it back right away.
Most tax agencies have regulations (such as the wash-sale rule) to prevent taking a capital loss in this fashion.
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