Anchor bolts set into the top of the pier.
The four anchor bolts were placed into the top of the pier shortly after the cement was poured. The bolts were held in place by a wooden jig and the upper right edge of the jig was aligned with a celestial north/south line which was determined in advance by GPS surveying techniques. True north is to the lower right of the picture. At this site, magnetic north varies from true north by two to three degrees. The jig is a duplicate of the metal Pier Extension Base Plate which when put in place of the jig will then be aligned with the north/south axis. Inaccuracies up to seven degrees on either side of the true north/south line can be adjusted for by turning the baseplate within curvilinear oval shaped bolt holes which are machined into the baseplate. Outlines of the baseplate bolt holes are scribed onto the top surface of the jig around each bolt.
