| 摘要 |
This invention pertains to a device having a first and second upright, a support rail connecting the first upright and the second upright, and a vertical spacer having a first edge, a second edge and a bearing surface. A height-adjustable leg may be provided between the support rail and the ground. The height-adjustable leg may be made of three(3) cooperating members, such as three interfitting tubes that may mate to form a triple walled support. A portion of the first edge of the vertical spacer is disposed on the first upright and a portion of the first edge is disposed on the second upright. A guide rail having a top surface is disposed along the second edge of the vertical spacer. The guide rail extends over the bearing surface. The device further includes a sliding support member having a first roller, a second roller and a third roller. The first roller engages the top surface of the guide rail and is oriented for transmitting substantially only vertical forces from the sliding support member to the top surface. The second roller engages the support rail and is oriented for transmitting substantially only horizontal forces from the sliding support member to the support rail. The third roller is disposed beneath the top surface of the guide rail and the first roller, and engages the bearing surface of the vertical spacer. The third roller is oriented for transmitting substantially only horizontal forces from the sliding support member to the bearing surface section.
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