| 摘要 |
An apparatus for positioning a movable object with respect to an immovable object is described. The apparatus includes a body with a top surface, a bottom surface, a first surface extending between the top surface and the bottom surface for engaging the movable object, and a second surface extending between the top surface and the bottom surface for engaging the immovable object, the second surface being opposed to the first surface. At least first and second contact points are defined by the first surface. At least third and fourth contacts points are defined by the second surface. The first and second contact points are separated from one another by a first distance and the third and fourth contact points are separated from one another by a second distance. The first distance is less than or equal to the second distance.
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