| 摘要 |
A spider for a railroad crossing signal foundation has plastic lined tubular channels extending through it with conical entry sections. In assembling a foundation, upright guide rods are guided into the channels by the entry sections without dislodging the plastic liners. In producing the spider, concrete is poured into a mold about tubular plastic liners so as to form entry sections and channels and to fix the plastic liners in the concrete to line the channels.
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