No problem brash, I'm glad that does what you need! Sorry I did not understand what you were asking about at first.

Also, when using perp/perp snap the initial point on the first curve must be somewhere in the general area (like with 50 pixels or something like that) of where the actual final point will be at. That helps to avoid it being triggered accidentally all the time, basically it only triggers if there was a shared perpendicular line in the screen area nearby both the first and the second pick.

If you have placed the first point very close to where the final perp/perp snap will be, you will usually find the activating point on the second pick to be just slightly to one side or the other of the "single perp" snap. You will know when you have activated perp/perp since you will see the label switch to "perp/perp" and it will also show on both points to indicate that both the first point and the second point are being modified by this particular snap.

The "single perp" object snap is different since it snaps the current point only, finding the perpendicular line coming directly from the base point. Perp/perp only uses your picked points as guides for where to look on the curve and the actual perp/perp snap locations come from a calculation that finds a shared perpendicular line between the curves.

- Michael