Jaw crushers are classified by the method of pivoting the swing jaw (Figure 6.3). In the Blake crusher the jaw is pivoted at the top and thus has a fixed receiving area and a variable discharge opening. In the Dodge crusher the jaw is pivoted at the bottom, giving it a variable feed area but fixed delivery area. The Dodge crusher is restricted to laboratory use, where close sizing is required, and is never used for heavy-duty crushing as it chokes very easily. The Universal crusher is pivoted in an intermediate position, and thus has a variable delivery and receiving area.