any way to flatten components along x,y,z,arbitrary plane?

I'm trying to find the command that allows me (in this instance) to flatten a group of border vertices along the Z axis.

Thanks!
DR

Hey dirtrobot,  welcome to the boards

as far as I know there are a couple of ways to do this..

1. Geometry > Common Commands n Tools > Flatten (which flattens to some arbitrary plane)
2. Use the Scale Gizmo with Orientation set to World (or you can set the axes manually with the 'Set Manipulator' visual streamline tool.

I think Voidworld by default will not allow negative scale operations.

You can try this one, Geometry > Common Commands n Tools > Align.

Many thanks!