Quote Originally Posted by reefy86 View Post
thing is though that really confuses me is when looking at the dimensions from zapp it just shows a diagram with an hole at 4.5mm, im not good at knowing what holes what but in solidwork i select m4 and it has a default settings at 10.10mm blind hole depth and 8.00mm tap thread depth.
As have been said A 2D drawing is best and if you are asking for holes to bolt the rails to, through holes are much easier to drill and tap. As long as the hole centres are marked and dimensioned on the drawing that will be fine. You can just say drill for M4 or M5 or whatever size you want, the company would then drill the appropriate hole.