Butler tray hinges with rounded ends are commonly seen on both new and antique tables. They are specifically designed for tables or trays with foldable leaves. Table leaf is held upright at 90 angle or held in an open flat position of 180. Placement of leaf is easily changed with a gentle push movement, once moved leaf stays in position.

Butler Trays supports table-leaf in upright 90 and flat 180 position

Keyboard Trays on Computer Desks Enables drawer front to open flat for keyboard, and fold upright when not in use