Originally this axis was designed to make ribbon twists which are done by tilting the router a few degrees. It later expanded into the ability to cut on the face of the work and a full blown Z-axis. The router can be used in several modes, vertical, horizontal and any angle in-between.
The angle of the router is made controllable by the use of a tilting mount made from aluminum. Screws lock the angle in place.
The Z axis is made by attaching Legacy's rails to the stock router tray with a pair of Legacy's bracket and some shop made ones for stability. The screw and split nut are also Legacy components. The photo below is taken from the back side of the z-axis.
An aluminum plate is used as a platform to hold the router mount.
For an example of what this attachment can do please see Bill's Candlestick project.