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The 5160 base is used with our alignment telescopes for making precise vertical sights, either upward or downward.  It consists of a clamp and level vial assembly, a bearing plate, and a leveling plate with three mounting holes which permit the complete unit to be mounted at a predetermined location.  The base is equipped with a circular level for rough leveling, and a coincidence level which reads to within 1 arcsecond.  The vertical line of sight may be displaced approximately 1¼" (31.8mm) laterally in any direction using the opposing pairs of thumbscrews for adjustment.

After being clamped in place, the telescope may be rotated for fine adjustments to the reticle orientation using the opposing brass thumbscrews seen under the top collar.

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At left, the 5160 plumb aligner base is shown holding a 2022 alignment telescope.  In use, the 5160 is bolted to any surface which allows for an upward or downward view, and which accommodates the mounting holes in the 5160's bottom plate.