Thank you very much Mark for your reply
we don't know who built this jig it's there for long time...
tha's what I'm trying to find out, the good reason, but so far nobody was able to give any,
I think because the roughing-out sump rail and cap-face before was done from a different machine, so may be they thought to machine just the 4 sides with the angle head and they thought to do so by raising the jig and then when they moved these new operations they thought to leave the jig like that, that's all I can think so far ...

who writes your machine code?

engineering manufacturing writes machine code, however also the programs are there for long time, so they do just some amendement sometimes

thank you very much again however I'd like more opinions about it