Typically, such a plan gives shareholders the right to buy more shares at a discount if one shareholder buys a certain percentage or more of the company's shares. The plan could be triggered, for instance, if any one shareholder buys 20% of the company's shares, at which point every shareholder (except the one who possesses 20%) will have the right to buy a new issue of shares at a discount. If every other shareholder is able to buy more shares at a discount, such purchases would dilute the bidder's interest, and the cost of the bid would rise substantially. Knowing that such a plan could be activated, the bidder could be disinclined to take over the corporation without the board's approval, and would first negotiate with the board in order to revoke the plan.