guide·post /-ˌpost/
  路標,路牌
  Guide·post n. A post at the fork of a road, with a guideboard on it, to direct travelers.
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  guidepost
       n 1: a rule or principle that provides guidance to appropriate
            behavior [syn: guideline, rule of thumb]
       2: a post bearing a sign that gives directions or shows the way
          [syn: signpost]