Not sure what this means:

C:\Program Files\Microsoft Games\Halo Custom Edition>tool collision-geometry scenery\sentinel_wall
Couldn't read map file './toolbeta.map'
### sentinel_wall.JMS
EAX: 0xFFFFFFFE
EBX: 0x002CC201
ECX: 0x0012F4C0
EDX: 0x000002CC
EDI: 0x0012F4C0
ESI: 0x00000000
EBP: 0x0012F398
ESP: 0x0012F388
EIP: 0x76DD6344, C3 8D A4 24 ?????
EXCEPTION halt in .\import_collision_bsp\build_collision_geometry.c,#979:
bsp3d_plane_test_point(plane, point0, NULL)==_bsp3d_plane_test_on

I constructed a series of boxes to represent the collision geometry of the sentinel wall from my map. None of the boxes are touching or intersecting, and there is no wrl to import (I previously had to deal with open edges, which I suspect were caused b the boxes being too close). Tutorials and instructions on creating custom physics files have been largely ambiguous, and I can't find the information I need to properly set this all up.

Isn't the sentinel wall part of your BSP?

It was/may still be. It was suggested that I make it a scenic addition, to make collision easier, and so I wouldn't have to design an elaborate sky geometry system to ensure all of the wall is included in the map. This will also allow me to better (and easier) tailor the length of the wall. Unfortunately, halo hates me, and did not create the collision model, and as if that wasn't bad enough, the visible model, which was built error-free, does not show in Sapien. Even the axes selector object is not visible when I place the wall. I haven't been able to determine the cause.

are you makung it a scenery?

Attempting to. As it stands, I suspect the size of my wall is too large, and thus causing my problem (it doesn't appear in Sapien). I can't figure out what's wrong with the collision. I tried using the model itself as the collision, and instead of getting open edge errors, I got the same error I posted above.

Did you try adding the wall as part of the bsp?
by detaching it as its own object and linking it separately to the frame?