I've figured it out, it appears Maya calls it Custom Pivot Point. Sorry for my bad explanation skills XD
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What I'm asking for is to change where in my selection does it snap to vertex or snap to grid.

So If I select a bunch of vertices, it will snap to the centre point of the selection, but I want to...

I'm a Max user and am trying to figure out how in Maya I can snap move an entire selection of vertices (or edges or polys) by clicking and dragging a specific vertex of my choosing from this...