Head Assembly - Top (ASM4)

[AskBud]

I have some questions about the Head Assembly - Top (ASM4).
Look at the attached picture.
1) What is the purpose of the potrusion on the shelf, in the red box, on the far Left?
2) What is the purpose of the two screw holes, circled, and what is the specification for the thread?
AskBud

[Dan-Woodman]

Bud
I 'm not sure about the two threaded holes . but the "box" used to have a senser attached to it for homing I believe in z position. There also was a removeable "flag" in the same area that senced home for "Y"position, . I think this is right , they were on my machine when I got it in 02-2006.
later Daniel