The putting green, or simply the green, is an area of very closely trimmed grass on relatively even, smooth ground surrounding the hole, allowing players to make precision strokes on it. To "putt" is to play a stroke on this surface, usually with the eponymous "putter" club, which has very low loft so that the ball rolls smoothly along the ground, and hopefully into the cup. The shape and topology of the green can vary almost without limit, but for practical purposes the green is usually flatter than other areas of the course, though gentle slopes and undulations can add extra challenge to players who must account for these variations in their putting line. The green typically does not include any fully enclosed hazards such as sand or water; however, these hazards can be – and often are – placed adjacent to the green, and depending on the shape of the green and surrounding hazards, and the location of the hole (which often changes from day to day to promote even wear of the turf of the green), there may not be a direct putting line from a point on the green to the cup.