Conceal a dagger in a smile

Corner potential  

White sacrifices the marked stone freely, but if the situation calls for it, there is still a hidden dagger - the aji - left in this stone. At an appropriate moment white may play a or b to destroy all the black territory. One must however be careful not to produce a weak group at the wrong moment.

See also 4-4 point one-space low pincer invasion, interception.