An auction is a process of buying and selling goods or services by offering them up for bid, taking bids, and then selling each good or service to the highest bidder. Participants bid openly against one another; each bid must be higher than the previous bid. In the activity described rather than goods or services, English teachers sell sentences! The activity can be an effective and enjoyable way to finish a lesson, to check students' understanding, and provide a review at the beginning of the next class. The main goals are to review a targeted grammar structure (or vocabulary or, at lower levels, numbers) and to give students a chance to work together and have fun.