| 摘要 |
Apparatus includes an upper plate assembly including a main portion, a first extension member and a second extension member. The extension members extending from the main portion at an angle. The apparatus also includes a lower plate assembly connected to the upper plate assembly, a first side plate, and a second side plate. The side plates connected to the lower plate assembly. Each side plate including a top and a bottom. The apparatus further includes an engaging assembly attached to the upper plate assembly and the lower plate assembly. Engagement of the engaging assembly causes the bottom of the first side plate to move toward the bottom of the second side plate.
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