Snapping in MC edit mode

How the heck do I turn this on?

Know what I mean, how when you are editing an MC, it doesn’t just autosnap when you are drawing new objects (if you start drawing a line, for example, it won’t snap to corners - but if you draw the line, then drag the endpoints, it will snap just fine).

I’ve searched for this problem so I apologize if it’s already been answered.