Gillette directors adopted an anti-takeover plan.

The plan, which gives shareholders the right to buy additional stock in the company at half price during a hostile takeover, was adopted even though company officials said they know of no such takeover threat at this time. The action will not prevent such a takeover but “will encourage any would-be acquirer to negotiate the manner and terms of any proposed acquisition with the board,” said Colman Mockler Jr., Gillette’s chairman and chief executive.