Prefixing names is often a confusing business, but I don't believe it has to be. Thus, here is my simplified instructions for prefixing names in a given Watchtower, using that of Air (ORO) as an example:
![Image](http://i148.photobucket.com/albums/s22/yechidah/watchtower-prefixes.jpg)
So, firstly we take the Horizontal Elemental Name of Air from the ToU: EXARP. This is the only name we use for prefixing on the Air tablet. The Kerubic Angels, whose names are above the Calvary Cross in each sub-angle are Spirit beings (however elementally biased they may be) and thus always take the Spirit letter of the Elemental Name - i.e. E in this case. Then the rest of the letters are taken in order and attributed to the Servient Angels of each sub-angle in the order of Air, Water, Earth, and Fire.
E is Spirit of Air
X is Air of Air
A is Water of Air
R is Earth of Air
P is Fire of Air
If we take the Kerubic Angel of the Air of Air sub-angle, RZLA, we would prefix it with E - thus, ERZLA.
If we take the Servient Angel of CZNS in the Air of Air sub-angle, we would prefix it with X - thus, XCZNS. This likewise applies for all the other Servient Angels in this sub-angle, and even the permutations of them (i.e. XZNSC, etc.).
If we use the Watchtower of Water (MPH), we would use the name HCOMA to prefix, and likewise for the others.
I hope this makes this seemingly complicated part of a complex system a little easier to understand.
LLLSHJ,
Yechidah.