| 摘要 |
A carriage with rollers for rolling it to different positions of adjustment along a track, and with means carried by the carriage for securely clamping it in adjusted position on the track. In clamping the carriage on the track, the carriage is brought to bear on the track and the rollers are raised clear of the track, and in unclamping the carriage, the rollers are lowered to engage the track and the carriage is raised clear of the track.
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