There are many types of adjustable leadouts. Perhaps the easiest is to buy a Brodak unit and install it.
http://www.brodak.com/shop_productde...ProductID=6622
To adjust a line, just loosen with a screwdriver, move and re-tighten.

Many rig a line guide with lines a fixed space apart having both lines adjusted together with one screw. Usually the spacing is about one inch.

My own preference consists of a plywood/balsa laminate that contains a slot for the wires to slide in and some holes for the eyelets that hold wires in position. I got this method from a Bob Hunt video. To adjust, you pull the eyelet out of a hole and press it back in another. The lines are adjusted individually. Here's a pic of my rig during construction of a Ringmaster:

George