stickhandling. Stiffness is also correlated to player strength; stronger players will often prefer stiffer flexes, as they have a sufficient amount of strength to fully bend (and thus maximize potential energy) using such shafts, whereas younger players and players with less strength will generally have more success using more flexible shafts which they are capable of bending to their optimal degree. Blade shape Until the early 1960s, hockey stick blades were typically not curved. However, in the late 1950s, New York Rangers center Andy Bathgate began experimenting with "breaking" his stick blades to impart a curve, which he found made his slap shots behave in highly erratic ways. Soon after Chicago Black Hawks forwards Stan Mikita and Bobby Hull stumbled onto the "broken blade", and subsequently began asking their stick manufacturers to create sticks with pre-curved blades. Soon after, much of the NHL, and Hull in particular, became a proponents of the "banana blade", or stick with extreme amounts (often up to ) of curve in the blade. These curves made slap shots behave very erratically, and in an era in which goalies did not wear masks, this eventually became an unacceptable danger. By 1967, the NHL began to limit the amount of curve a stick blade could legally have. In the NHL today, the legal limit is 19 mm, or of an inch. Much like the shaft's flex, a blade's shape is a very important characteristic of a stick's performance. There are three primary variables in blade design: curve, face angle, and toe. The curve refers to the basic amount the blade curves from toe to heel, as well as the part of the blade where that curve is located. A "toe curve" means that the curve is concentrated near the toe of the blade, and it is usually preferred by forwards, who seek better puckhandling and more accurate wrist shots. A "heel curve" is generally better for slap shots, and is thus used more by defencemen. Face angle is the angle between the ice surface and the front surface of the blade (this characteristic is comparable to the difference between the different irons in golf). A more "open" blade means that the face of the blade is turned up more sharply, and thus will cause a higher trajectory than a "closed" face angle. The toe shape refers to the basic shape of the end of the blade, and