Installation seems simple enough-- Point the heads straight out and level in both planes.
Level requires only a small bubble level and shims. But what about pointing straight? In order to point straight one would need a frame of reference on the front of the car itself. The reality, however, is that there usually are not any flat surfaces on the front of the car.
So far, all I can think of is to use a level or other straightedge and attach "sticky notes" or the like to it and then hold it up againt the plate, which should arguably point straight ahead. The sticky notes act as extensions, which I place so as to just contact the heads, which in turn allows me to adjust the heads until they point approximately straight. Of course, this assume that the heads are more or less in or near the sdame plane as the plate.
Does anyone else have any better ideas or methods? I ask this as I noted that the heads on my wife's Sienna van went all out of whack for reasons unknown. Tough to install on this van due to all the curves and dearth of good mounting locations. Despite rigorous cleaning and prep the double sided tape used to anchor the heads to the brackets loosened. Damned annoying.....