An advanced deposition technique known as glancing angle deposition (GLAD) [K. Robbie, J. C. Sit, and M. J. Brett, J. Vac. Sci. Technol. B 16, 1115 (1998); K. Robbie and M. J. Brett, U.S. Patent No. 5,866,204 (filed 1999)] has been used to fabricate periodic arrays of magnetic pillars and randomly seeded magnetic helices, posts, and chevrons. Because of the nature of initial film nucleation, the CLAD process normally distributes posts randomly on the substrate surface. We can grow periodic arrays of GLAD microstructures by suppressing the randomness inherent within the initial nucleation stage of film growth. Shadowing sites were fabricated by pre-patterning a thin titanium layer on silicon substrates into a square array using electron beam lithography. These sites shadow regions of the substrate from incident flux during film deposition and act as preferred nucleation sites for film growth. Using this process, we have fabricated periodic arrays of cobalt posts with a regular elemental period of 600 nm and post diameters and heights of 300 and 400 nm, respectively. Randomly seeded posts, helices, and chevrons were also fabricated. The mean separation for the randomly seeded posts was 350 nm with individual post diameters of 100-150 nm, while the separations for the helices and chevrons were less than 100 nm. X-ray diffraction, transmission electron microscopy, and a de superconducting quantum interference device magnetometer were used to analyze the magnetic and crystal properties of both the periodic and randomly seeded arrays. A newly developed three-dimensional ballistic deposition simulator was used to simulate the growth of the periodic post arrays in order to better understand the growth mechanisms.