witness-post
 n.— «It is extremely important that the points S and L of each spiral should be secured by permanent monuments in the centre of the track, and by witness-posts at the side of the road. The posts should be painted and lettered so that they may serve as guides to the trackmen in their subsequent efforts to grade and “line up” the track.» —by William H. Searles The Railroad Spiral (New York) , 1882. (source: Double-Tongued Dictionary)

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