Use small steps to keep plates aligned?

When building a CNC Router and you needed to mount a vertical gantry plate to a horizontal plate, that attachs to the Linear rail and ballscrew block, would you machine a small 'step' in the base plate to ensure correct placement/alignment of the the 2 parts?
It seems to be a good idea, but i'm not sure i have seem too many people do it. Just wondering if there is an obious reason not to do it.
No adjustment avaialble?
Steve
Attachment 431756

Like you,it isn't something I have seen and I don't think I would take the time to do it.On the other hand I would add a web on the outside of the sectional view you posted, in order to keep the vertical plate from flexing.

Thanks Routalot,

I wouldn't think it would take much to machine a small step in ones Gantry plates and the step would 'lock' the plates in position.....Maybe its too fiddly.
I was thinking the same re:web.. Would not want to rely on that fixing to be and stay 90°.