If, in phnx.par you set quarter_sector = 1, then only a quarter of the North endcaps are turned on.
Source used: svx.f.

This picture shows the silicon panels only, plus, for orientation, the innermost layer of the barrel, plus a test volume that starts at (0,0,0) and extends into the +x, +y, +z direction. +z points North, +y is up, so +x is to the West. The bottom image is a view looking North. Note that the 6 panels do not start at +y, but are rotated to match the Muon arm pattern of frames and blockages, shown below. quarter.kumac

(from mu.html)