Elevator Trim
Take a look in the forum area for the model you're thinking of buying...then click on the "Show us your panel !!!!" link. You'll be able to scroll down the thread and see numerous examples of control layouts.
In general, the manual trim knob is the largest black knob on the panel. Most builders elect to put it near the throttle quadrant. On the RV8/8A it is usually slightly above and forward of the throttle (on the left side of the panel). On the RV7/7A I've seen them above and below the throttle, depending on whether or not the builder has a center console setup.
The manual trim works well. Having said that, most of the RV builders I know (including me) have opted for the electric trim so they can wire it into the stick grip(s).
Good hunting,
Mike