You can use a flat head screwdriver or a 10mm socket - here are 2 other posts on adjustment: http://club.vmag.com/ubb/Forum39/HTML/000289.html
http://club.vmag.com/ubb/Forum39/HTML/002249.html

It helps if you can aim at a garage door or wall and see where you are adjusting - please err to the right as opposed to blinding oncoming traffic.