The OSNAPZ command comes in so handy at times. Sometimes when you are trying to snap from an object/point that has a Z-coordinate, the Z-coordinate can mess things up, especially when you are working in a 2D drawing and you don’t care for the Z-coordinate.
For instance, you overlaid a 3D model over a plan drawing, snapping to that model will cause that line to not be parallel to the XY plane, but will get a Z-coordinate. Other instances could be when measuring in the XY plane in survey drawings (which will most likely always have a Z-coordinate for the surveyed objects); snapping from a surveyed point to any other object won’t give you the dimension in just the XY plane, especially when you have rotated your UCS as well (this happens a lot when working with multiple coordinate systems).
Well, there is an easy fix for this, with the OSNAPZ command. As explained in the AutoCAD User Documentation:
“Controls whether object snaps are automatically projected onto a plane parallel to the XY plane of the current UCS at the current elevation.
0 – Osnap uses the Z-value of the specific point
1 – Osnap substitutes the Z-value of the specified point with the elevation (ELEV) set for the current UCS”
So, by default OSNAPZ is set to 0, which means you will snap to whatever the Z-value of a specific point is. If you set it to 1 it will (by default) consider all Z-coordinates to be 0. Meaning you will always be snapping to the XY plane, and a 2D drawing, will stay a 2D drawing. You won’t be introducing weird Z-values in you drawing (which you might want to flatten in the end otherwise…).
The default elevation (Z-value) is set to 0 (for your current UCS), but you can change that as well with the ELEV command, if needed.
I use this very frequently. It saves me a lot of frustration in my workflow, and most especially, keeps my 2D drawings, two dimensional!