| 摘要 |
A first horizontal elongated plate has a longitudinally extending slot therein. Each of a plurality of vertical L shaped members has a bottom horizontal leg disposed at right angles to the slot and an upwardly disposed vertical leg. Each of a like plurality of soft yieldable elements is manually slidable in the slot, each horizontal leg extending through a corresponding element and overlying the top surface of said first plate. A second horizontal plate is secured to the top surface of the first plate, said vertical legs being disposed adjacent one edge of the second plate, said first and second plates having regions spaced apart to permit said members to be slid back and forth along the slot. A third horizontal plate is secured to the first plate remote from said members, adjacent parallel edges of said second and third plates being spaced apart to define an opening parallel to said slot through which said vertical legs extend.
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